As ever, the Touch ID fingerprint sensor lives in the iPhone's home button, but this year's module is a clear improvement: Apple claims it can pick up your fingerprints up to twice as fast as before. I can't make out exactly what the speed multiple is here, but Touch ID really is blazing fast now, and I can't remember the last time it didn't work on the first try, either. In fact, it's actually so fast that I've had to change some of my daily behaviors as a result. You see, I used to be one of those people who tapped on the home button to check the time or change tracks while I was in my car (yes, dangerous, sorry). With the 6s and 6s Plus, that doesn't fly anymore: Touch ID picks up all but the quickest home-button taps.

As it happens, both phones are a touch thicker and heavier than before, but they're still comfortable to hold, and the change in thickness specifically is so subtle that it's nearly imperceptible. As for the weight, the 6s and 6s Plus do indeed feel noticeably weightier: The 6s weighs in at 143 grams, up from 129, while the bigger 6s Plus now comes in at 192 grams, up from 172. Not that that's a bad thing. All told, this is one of the few times an iPhone has gotten beefier (the 4s was slightly heavier than the 4), and I'm actually quite pleased about it. At some point, there has to be a lower limit to how thin a phone can get and still be comfortable to use. I'd much rather see companies abandon that ceaseless march toward cartoonishly thin designs and instead work to make better use of the sizes they've already achieved. Bigger batteries, anyone?

Speaking of the sort, the cells in these new models are actually slightly smaller than they were before: 1,715mAh in the 6s and 2,750mAh in the 6s Plus. I'll delve more into battery life a little later (spoiler alert: It hasn't really changed), but recent teardowns seem to reveal why we've gotten a bit of a downgrade this year. In short, you have that new 3D Touch screen to blame. To give you a little background, the display crams 96 pressure sensors into the backlight layer of the phones' Retina HD displays, along with a Taptic Engine that provides some subtle vibrations when you bear down on the screen. Turns out, the engine took up some extra room near the phones' bottom edges, just under the spot where the battery sits. For now, the time-savings you get from using 3D Touch gestures feels worth the slightly smaller batteries, but hopefully Apple will eventually figure out how to shrink the necessary components so that it doesn't have to compromise on battery size.

A new display, and a new way to touch it

At first glance, you probably wouldn't notice anything different about the IPS screens on the 6s and 6s Plus. After all, they're the same size as before (4.7 inches and 5.5 inches, respectively) with the same pixel density (326 ppi, or 401 ppi on the Plus). You won't even notice the improved glass covering them until you drop it (please don't). The eagle-eyed among you might catch that both screens are a touch brighter with slightly better color reproduction. There is, of course, something much more important at play here. It's called 3D Touch, and it's the biggest change in how we interact with iPhones since Siri.

Let's start with the broad strokes: If you press your finger down on, say, an app icon, you'll get a small menu of quick actions that you'd usually have to be inside the app to use. You'll also feel a brief vibration from the Taptic Engine as a sort of tactile "thumbs up." Like any new behavior, applying force to your iPhone's screen will take getting used to. The whole thing is made a little trickier by the fact that it's initially easy to mix up a 3D Touch and a long-press (like the one used to rearrange your app icons). It didn't take more than a day or two for my muscle memory to learn the amount of pressure needed to make 3D Touch work, but hey -- your mileage may vary.

Those 96 3D Touch sensors can also take precise measurements as you push down and release. Imagine, for instance, playing a racing game and being able to press the screen to accelerate past the chump who just whiffed while taking a corner. If that's the future of smartphones, bring it on.

What's more, there's an entirely new vocabulary around this 3D Touch screen. Pressing down to preview something in a little pop-up window -- be it a web link, or an address someone texted you -- is what Apple calls "peeking." Apply just a bit more pressure and the phone will bring up the usual, full-screen app view, in this case a Safari window or a location in Apple Maps. Congratulations, you just "popped" something. You can't use all the same 3D Touch actions if you're using an iPhone 6s Plus in landscape mode. Pressing down on app icons still brings up the menus you'd expect them to -- as evidenced by the GIF above -- but you can't peek/pop addresses or hyperlinks in Messages and Mail while the phone is sideways.

Apple's already laid out guidelines about how developers should implement 3D Touch, and they're basically centered on one key idea: 3D Touch is about helping users do things faster. So far, the vast majority of apps don't yet support 3D Touch, but the ones that do take different approaches as to what you can peek at. Some, like Twitter and Instagram, let you press down on their app icons to bring up those Quick Actions menus for near-instantaneous tweeting and photo sharing. Others, like Dropbox, offer previews of your files when you long-press their filenames in a list, but there's no app icon interaction. OpenTable takes sort of a hybrid approach -- you'll get both an app icon menu and the ability to peek at restaurants' locations in Maps as you're scrolling through the culinary options.

This all might sound complex, but trust me: It's not. Once more developers get on board, people will be able to zip around their home screens and just do things, as opposed to constantly jumping in and out of apps. It's also a tremendously useful tool for getting quick bits of context -- why yes, I would love to see a map of that sweet poutinerie in Berkeley, thanks very much.

After I got used to using 3D Touch, going back to the plain screen on my iPhone 6 was almost painful. Heck, even if you use the 6s and 6s Plus full-time, most developers haven't had the chance to build 3D Touch support into their apps yet. I can't tell you the number of times I was reading something in a non-supported app like Twitter, and pressed my thumb down on a link only to have nothing happen. Whoops! The mild twinge of annoyance I felt every time that happened speaks to how powerful 3D Touch is: It might seem like a gimmick at first, but it quickly became a feature I wanted to use all the time.

Software

I've already penned a few thousand words on iOS 9, and its focus on cohesiveness and efficiency makes a great match for the new iPhones. Most of the software tweaks on the 6s and 6s Plus are centered on those lovely little 3D Touch interactions, but there's one more trick that's currently only available on these things. Jump into Siri's settings and you'll find that you can now enable "Hey Siri" -- Apple's always-on listening mode -- to work even when you're not connected to a power source. The feature launched with iOS 9 just a few weeks back, but it works best with the new iPhones' more efficient M9 co-processor helping out under the hood. Weird as it sounds, I've taken to just talking to her sometimes when I want to listen to some Capital Cities in Apple Music, add yet another event to my stupid-packed calendar or turn on Airplane Mode when it's time for some shut-eye.

What's more, one of my favorite features from recent iPads has reached the new iPhones: 3D-Touching the keyboard while pecking out a text turns it into a trackpad for precise placement of the cursor when an inevitable typo pops up. If you lump in these tweaks with all the other thoughtful design changes in iOS 9, you're left with a tightly integrated package that tries to give us the apps and info we want at just the right time.

Camera and Live Photos

iPhones account for a huge chunk of the photos taken every day, so it's no surprise that Apple takes this camera business seriously. Thankfully, after several years, Apple finally traded in its 8-megapixel sensor in favor of a 12-megapixel main camera. Naturally, it's actually not so much the higher resolution that matters; it's all the other, more technical bits that should help improve photo quality. The folks in Cupertino went for smaller, more densely packed pixels (1.22µ, down from 1.5µ in the iPhone 6) that make for higher-resolution shots... with the added potential for more noise.

That's where Apple's "deep trench isolation" comes in: The company managed to separate the sensor's photodiodes to keep incoming photons from introducing interference into surrounding diodes. You don't really need to worry about that, though: It basically just means your photos should come out nice and crisp. Pair all that with a five-element lens and a familiar f/2.2 aperture and we've got ourselves another serious camera contender.