First things first (and this should go without saying): Don't install the Android M preview and expect to see all the whiz-bang features from the keynote working in perfect harmony. They won't, mostly. As was the case with the Android L preview from last year, this isn't a build meant for wowing your iOS devotee friends. It's about giving developers an early chance to hook their apps up to Google's modified vision, so Android Pay, Direct Share and almost all the rest are nowhere to be found. The most crushing omission in my book is the lack of Now on Tap, a conceptually dead-simple feature that provides an informational Now card based on what you say or what's on screen. I fell in love so hard with this feature that its absence is almost palpable -- some might call it creepy, but I'm more than happy to let Google decide what I want before I can.
So what is there to pay attention to? Well, there's a revamped app launcher, for one. Instead of the discrete cards displaying your apps you swiped through in Lollipop, you're now left with a scrolling list with apps lumped together by name. The four apps you use most often live in an ever-changing top row that does a good job keeping up with your changing moods. The quick-launch bar also makes an appearance whenever you type something into the Google Search widget, although I can't honestly remember the last time I needed to search for something online and jumped into one of those apps instead. If you dig into the developer settings, you'll also find a System UI tuner that -- for now -- only lets you rearrange the Quick Settings slots that live above your notifications shade. Device makers like LG have let us fiddle with these little bits for ages now, and it's nice to see Google take inspiration from what others have already done to Android. (You could also be a contrarian at look at this as Google cribbing notes from OEM innovation, but that's a debate for another time.)
One of Android M's other big draws is its much smarter take on app permissions -- the days of agreeing to permissions before you'd even used an app are over, or at least they will be down the road. You'll still have to sign off on a manifest of permissions requests, but you can jump into the Apps menu in the settings to manually disable certain permissions. Sorry Airbnb, you're never touching my camera again. As you can see in the above screenshot, Android is going to nag you; after all, most of the applications you'll try this trick on won't play nice.
I left most of my apps well alone, but I spent more than enough time coming to grips with Google's improved sound and notification controls. You see, in the days before Lollipop, you could crank your volume all the way into a vibration-only mode, and one more click would make the phone completely silent. Now, with M, that one last click brings you into a Do Not Disturb mode that you can play with from the Quick Settings shade. Android's original implementation felt damned-near perfect, but M's is a step in the right direction: More often than not I'd just leave things in Priority Only mode so I could filter everything but work messages.
Beyond all that lie mostly minor changes: Your lockscreen font is a hair thicker than it used to be, and swiping from the left corner of your locked phone's screen brings up Google's Now voice interface instead of the dialer. If M's insistence on white interface elements is doing a number on your retinas, you can fire up a dark theme... but that only changes the way the settings menu appears.
Now, let's take a moment to step beyond what's new: How well does Android M as a package actually work? If you used the Android L preview as your daily driver right out of the gate last year, you were in for a world of potential, unstable hurt. That's not at all the case this time: My sacrificial Nexus 6 generally ran as well as it did before I started fiddling with it. Nearly all of my apps were peachy after re-install, though you'll run into lagginess and force quits more frequently than before you took the plunge. Some users have reported that their 64GB Nexus 6s were only reporting 23GB of storage space, but you can apparently fix that with a spin in the command line. Just par for the course, chums.
Thing is, when M works well, it works really well, which makes those moments of computational confusion stand out even more. Case in point? My T-Mobile LTE connection worked like a charm, say, 90 percent of the time. There were a few puzzling moments when I'd see the cell signal indicator go completely dark and my connection would go dead even though I had full service just moments before. Sometimes a quick restart would coax the connection back to life, but more often than not, I just had to wait for it to decide to work again. Oh, and once or twice while using the Nexus 6 as a mobile hotspot, I kept getting routed to Google Ireland whenever I tried searching for something -- I still haven't figured that one out. None of these issues has gotten to the point that I'd call them dealbreakers, but they're probably just enough of a headache to keep novices away.
As I've mentioned, if you can scarcely wrap your head around a command line, you probably shouldn't muck around with Android M yet. It's far from finished, and it strips away the sort of polish you'd want out of a device you carry around on the regular. Here's the kicker, though: If you don't mind the occasional (and usually very temporary) headache, the Android M developer preview makes for a thoughtful, mostly stable day-to-day companion. When I first fired it up, I was more surprised at how whole it feels rather than how incomplete it actually is. Several days in, that feeling hasn't disappeared.