A day after Microsoft showed off an early version of its user interface for Windows 8 -- and I've actually had a chance to actually see it (via videos and photos) -- I've got mixed feelings.

For tablets, I like the tiled interface that looks like it has taken its cues from Windows Media Center and Windows Phone. I've used the tiled interface on Windows Phone and I think it will be a great way to navigate Windows 8 when installed on a touch-first/touch-centric device.

For PCs, I am not so sure -- especially for legacy PCs, like my two-year-old ASUS thin and light laptop. Why would I put Windows 8 on this non-touch-centric machine? Yes, I heard Microsoft execs say that the so-called Modern Shell (MoSH) will allow users to interact with a keyboard and mouse. And I believe users will be able to switch between the touch-centric mode and a more traditional Aero interface mode with Windows 8. But why should the default interface, optimized for gestures and touch, be required on a machine that I never plan to put my grubby fingers on? Some good places to see the new Windows 8 UI:

Istartedsomething.com

ZDNet

Microsoft's "Building Windows 8" video

Engadget

Microsoft made it clear last night that -- contrary to expectations and rumors -- the new shell is going to be the default on all Windows 8 PCs, and not just tablets. Many of us Microsoft watchers had believed it would be the default on tablets.

If I am a business user with Windows Vista or Windows 7 installed on my existing PC, will I want to upgrade to a touch-centric Windows 8? Even if it has faster startup/shutdown/hibernate, a better built-in data-recovery mechanism, or a Windows Store for purchasing/keeping track of my apps? I'm not so sure.

I'm starting to wonder whether Microsoft has decided to target users who are planning to buy new PCs preloaded with Windows with Windows 8, and to just let the existing base stick with an older version of Windows. Given the emphasis by Microsoft execs during the June 1 demo of Windows 8 on the new kinds of immersive applications that will be possible with Windows 8, it does seem that Microsoft isn't thinking about users with legacy/line-of-business apps with its coming Windows release.

(And as one of my readers noted, if you're a developer, do you now write apps to work with Windows 8 "legacy" mode or Windows 8 touch-mode? Maybe Microsoft's decision to push HTML and JavaScript as the way to write new Windows 8 apps dictates that decision for you....)

On the Windows 8 ARM tablets that are coming, Microsoft officials have said there will be no compatibility later enabling existing Windows x86 applications to run on those devices. (That's why Microsoft is having to rejigger Office to work natively on ARM-based Windows 8 tablets.) On x86 Windows 8 PCs, there will be support for (some? all?) apps and peripherals that currently run on Windows 7, according to Microsoft's own statement:

"We also showed effortless movement between existing Windows programs and new Windows 8 apps. The full capabilities of Windows continue to be available to you, including the Windows Explorer and Desktop, as does compatibility with all Windows 7 logo PCs, software and peripherals."

(Microsoft hasn't yet confirmed how/whether it plans to include some kind of virtualization technology as part of Windows 8, allowing users to run older legacy and line-of-business apps.)

For a company that has tried to blur the lines between tablets and PCs, I guess Microsoft's new touch-optimized shell interface makes sense. But for a company that continues to play up how many more PCs are being sold than iPads and Android tablets, the new Windows 8 default UI seems like somewhat of an odd choice. As my ZDNet colleague Larry Dignan asks, "Can Windows 8 really do it all"?

What do you think?