I've been running the (final) image for a few days now (non public channel) and I can say with certainty that this is the most relevant development to ever happen to Android. The jump between Android 4.x and 5 is about as big as the leap between iOS6 and iOS8. There are some people who poo poo Material design, but on an actual device (Nexus 5... and such here) this thing is just goddamn beautiful and has taken a lot of "ease of use" cues from other platforms and plugins to make this clearly and without question the defining moment in the evolution of Android.
Android 5 can stand its own against iOS8, and outside of Coherence and similar OS X Yosemite integrations - Android 5 is a true best of class OS. While I've been a user of all of the platforms for a while, I'm really excited about where Android is going with this next release.
I'm hesitant to say that I think Google's larger strategy with Android is the best move (no comment, but listen to their strategists), but they are definitely making this a "Google First" platform more and more with each release. How that echoes through the rest of the food chain will be interesting to watch.