(Pocket-lint) - Microsoft Surface is one of those products lines that's neither quite here nor there. But the Surface Pro 3 looks to change that, by refreshing the range in a new, larger 12-inch model that Microsoft has referred to as a "laptop killer".

Cleaner cut marketing than before, the Surface Pro 3's message is altogether clearer. With full Windows 8.1 on board - gone is the horribly confusing Windows RT option that the first Surface device mistakenly adopted, and good riddance - this is a laptop-quality device in upscaled tablet form.

But with its not inconsiderable 12-inch screen size has the Surface Pro 3 gone overboard in terms of physical size, or does it successfully walk the line between "the best of a laptop, best of a tablet" as it proclaims and, indeed, is so desperate to finally achieve? We've been using the Surface Pro 3 for a week ahead of its UK launch to see whether Microsoft has finally cracked it.

The earlier Surface Pro devices weren't exactly small by tablet standards, they existed in an odd "fat tablet" position while offering less screen real estate than a laptop. They didn't sell well, so Microsoft saw that something had to change: the physical size and target market.

The Surface Pro 3 plants a 12-inch screen in a 292mm x 200mm frame that's just 9.1mm thick. To put that in perspective: it's slimmer than even the latest Nokia Lumia 930 smartphone, but it's not in the same league as the 6.4mm thick Sony Xperia Tablet Z2.

But that's because the Surface Pro 3 is a different kind of device. Even though it looks like an oversized tablet, its Intel Core i processor architecture is on a level with laptops - hence the thickness for necessary hardware cooling vents - and the Windows 8.1 operating system is identical to what you would get on any up-to-date laptop too.

However, the Pro 3 is a sort-of laptop because straight out of the box there's no keyboard included - a moan we've had about every single Surface device to date - so you'll need to buy one for an additional £109 for it to be a true laptop replacement.

With the keyboard clipped into place via the magnetic connector it folds backwards to double-up as a screen protector, and very nice it feels too. But with it included you can add to the thickness measurement by a couple of millimetres and the otherwise lightweight 800g mass increases to 1.1kg, putting it in similar size and weight territory to the 11-inch MacBook Air.

The Pro 3 does include a stylus in the box, which will be of significant use to some users and next to useless for others, which does leave us wondering why this wasn't the optional accessory and the keyboard came included in all purchases instead (this is the first 12-inch Surface device after all, so older keyboards won't fit the scale). Unlike the earlier stylus which featured a magnetic connector there's also absolutely nowhere to store the Pro 3's one so you'll be forever losing it or digging into bags and pockets to try and retrieve it.

So it may be bigger than before, but there's the familiar Surface relic of "is it a tablet, is it a laptop?" about the Pro 3. Once again, it's a device trying to straddle two camps.

In resolution terms that 12-inch panel isn't messing around, delivering 2160 x 1440 pixels of quality. However, not all programmes will always tap into that resolution, as we've seen Chrome updates show pixelated text or icons in some cases, as one example of a handful. Typically everything is on point and looks crisp - it's down to the apps to deliver the content in the right format.

Viewing angles are also great, with the brightness, colour and contrast maintained throughout multiple angles, even obtuse ones.

As the Surface Pro 3 is a relatively large device you're less likely to hold it as a tablet, though, and it's here the integrated stand comes into great use. Unlike the single-position original or two-position-only follow-up, the Pro 3 has got it right third time around: pop the stand out to its minimum stand-sufficient distance and then it can be flexed further back to the nth degree. That finally means you can rest the Pro 3 on your lap with just a slight upward-facing angle, or pop it on a table and have it sat anywhere from flat to almost directly upright.

But there's a problem: Microsoft has opted for a glossy screen coating. There's rarely a moment that you won't be staring back at yourself when indoors in even diffused daylight, trying to avoid making a face at your own reflection. It's like trying to look beyond the reflective layer in some magic eye poster. We can't remember the last laptop we used that was like this; tablets, sure, but the Surface Pro 3 was supposed to be a step beyond and this particular shortcoming has really got to us. Not one for outdoor use for sure, and even when using it at night there's still a hint of reflection.

What the Surface Pro 3 can't be accused of is lacking in power. There are loads of options available and you'll want to pick wisely as to which suits for a number of reasons.

Firstly there's the on-board storage, which begins at 64GB in the basic model, but you'll lose around 30GB of that to the system (as if the 96.5GB available on our 128GB drive shows). There's a sort-of workaround in the form of a microSD slot, so you can buy a card up to 128GB now for a nominal sum.

On board capacity options push through to 512GB maximum, but each jump is paired with an increase in processor power, integrated graphics and, therefore, price. And the Pro 3 gets rather pricey. The £639 Intel Core i3 model with 4GB RAM and 64GB storage totals £750 once the keyboard is added. Top of the stack is the Intel Core i7 processor with 8GB RAM and 512GB of storage - which is a over a full £1,000 more, at £1,649 before adding the keyboard.

Our review model is a step up from the basic: the Intel Core i5 model with 4GB RAM and 128GB storage, with an £849 asking price, totalling £960 with the keyboard. But that put a question in our mind: why not save £109 and buy a 13-inch MacBook Air instead?

Comparing the two does make clear the difference between these products, as the Apple device (without stating the obvious it runs OSX, not Windows) is roughly twice as thick, doesn't offer a touchscreen or stylus, and delivers less resolution. However, it does have better battery potential, a non-reflective screen and is more affordable. Different devices, different audiences, varying suitability, but put like that and we can see how the Surface adds its own points of differentiation to be an attractive product.

However, no Surface Pro 3 model includes Microsoft Office in the price which we think is more than a bit stingy. This is a Microsoft product after all, the same company that makes the software, and when even £350 Windows 8.1 machines often come with Home & Student edition it adds an extra sting. Perhaps the company is trying to shake off the assumption that it's a "businessy" company.

We started to write our Surface Pro 3 review after receiving the device, but some days later - and having adopted it as our replacement device (a pain with the lack of Office) - we can see the appeal of this laptop replacement. Because, for us, that's exactly what it has become. We've even been avoiding using the touchscreen most of the time, as it's not something we typically need to do, plus that glossy screen coating is a stickler for fingerprint marks that catch the light and look prominent.

The keyboard is the clincher to the package for us. Although there's a little more "bounce" when typing on a lap compared to a regular laptop - a given as the two components of the device are separates - the depressible keys are of ample size and make for a comfortable typing experience. Even the trackpad feels responsive despite offering a smaller size than what we're typically used to, which can impact two-finger scrolling gestures somewhat.

But the more we've been glancing at the Surface Pro 3 arranged in this laptop form around the house the more we've been thinking to ourselves that it is just a laptop. Some of the tablet features are lost on us because of the device's sheer physical scale. It's almost a foot long, all in, and despite ample finger-width bezel surrounding the screen on all sides, we've not found it of much use to hold as a dedicated tablet. So the "best of tablet" part of the marketing campaign we're not sold on.

But the size will makes sense for some. Much like the Samsung Galaxy Pro 12.2 which is similarly large, it's with the stylus-based control that a certain audience's eyes will light up. And much the same can be said about the Surface Pro 3 we suspect.

It's taken a while for Windows 8 to settle down and become a more familiar operating system for many. In its 8.1 guise it's easy to utilise the device in a similar desktop-only way to Windows 7 if you want, or go touch-crazy and live in the Windows 8 Start menu instead.

Installing any software is no problem either. You can download executable files through a browser, just like you would on a laptop, or go in via the Microsoft Store app which delivers a more tablet-esque source for games, apps, news and so forth.

That translates well in use, from video playback via VLC, to browsing using one of many possible browsers, and all the usual laptop stuff such as Skype calls and conversations. The only system hiccup we've spotted was an occasional delayed response to virtual key entry, typically when using the inbuilt search option. An oddity.

As there's plenty of screen space to play with it's possible to load multiple applications just like you would in Windows. Easily adjust their size with the mouse pointer, or physically by touching and dragging on the screen. A good example was Skype sat next to a browser window for chat and browsing multi-tasking without needing to tab between windows.

The Surface Pro 3's graphics, which are integrated with the processor chipset, begin with Intel HD 4200 for the i3 model, then step up to HD 4400 with the i5 processor and HD 5000 with the i7 processor. No discrete graphics to be found here, nor next-step Intel Iris, but we've found there's just enough power in the i5 Pro 3 to just about load up proper games.

Well, we say proper, if Goat Simulator can be considered that. The title, launched through Steam, ran at a usable frame-rate around the 720p mark. When asking the Pro 3 to deal with heavier tasks such as this it will run really hot though, and when the cooling fan kicks in it's just as noisy as a laptop, not quiet like a tablet.

But it wasn't just mayhem by goat that we got into, as we found in this gaming example that the default lowest resolution also applied itself to the entire operating system. So after closing Steam we had to dig through giant icons and an enlarged Start menu to get to the settings and drag the resolution back up to its 2160 x 1440 best again. Oh, and if you happen to make the orientation rotate by accident during play than that too can cause issues with the screen hanging in blackout.

Such heavier tasks will inevitably also impact on battery life, cutting down the Pro 3's nine hours per charge longevity depending on what you're running. But we didn't spend much time gaming, as a work-based laptop alternative the Pro 3 gave us a full office day on a single charge no problems. It's not as strong as the MacBook Air we're used to, but that nine hour mark is realised in use and that's as much as many will need.

Verdict So is the Surface Pro 3 the "laptop killer" it claims to be? It's not out and out murder, not even manslaughter really, more a viable laptop alternative with full Windows 8.1 that will suit a certain audience. Just like its earlier Surface predecessors, the Pro 3 still sits on the fence with what exactly it's trying to be - and it doesn't succeed in delivering the best of a tablet device given its 12-inch scale. It's also expensive, there's no MS Office included in the price and the screen has an annoyingly reflective coating. But despite finding this physical size perplexing at first, a week of use in the laptop form (and with the optional keyboard attached, of course) has come to make sense. Often great sense thanks to the significant screen resolution and multi window multi-tasking, variable position stand, touchscreen controls and included stylus. It's clear the Pro 3 is the most accomplished Surface yet, but it still won't tick all boxes for all users.

Writing by Mike Lowe.