I tried using it as daily driver, but eventually switched back to 5.1.1. There are occasional bugs here and there, my major problem was with OK Google not working the right way and battery percentage not showing correct value (quick google search will show you it's common issue). Some apps didn't work (like Snapchat), and after updating apps in google play store you couldn't press the "back" button, you had to hit "home" etc. On a positive side, feels veeeery smooth (except for random freeze once in a while), animations are great, battery seems to improve, even with that display bug, charges a lot faster, etc. I'll wait for preview 3 and probably use that as my daily driver.