I’ve been using it on a Nexus 5 since… I suppose November 2014… and it’s decent. More recently, the random crashes have been getting a lot worse; primarily after being on a Hangouts voice call for a while, or when taking pictures.
Earlier on, whatever process controls the homescreen/launcher kept getting evicted from RAM, so it’d have to reload every time I went back to the homescreen after entering essentially any app, which was pretty silly.
I like the overall direction the UI is going. Improved consistency.
I am thinking of jumping ship, though. Primarily because of Swift, but also because iOS is now tinkerable-enough for me to be able to stand it on a daily-use device.