I say:
DON'T BE TOO QUICK TO UPGRADE (at least, an ASUS Nexus 7 (2012 ver)) to 5.x.x
I find it's too slow; you'll lose color & background config., & some apps break.
OK, apps can be updated (eg, CBC was quick to fix "CBC Radio" for 5.x.x), but who wants to be [effectively] "forced" to upgrade their hardware before they want to?
Look around, see if any others are "in pain" from their decision to move to 5.x.x
Even Mail's slowed down, possibly on 4.x.x systems, no less…
Google seems here to be acting like Apple, & I don't like it at all.
Tell you your experiences, below, but be sure to list your Hardware details.
Use our Poll & clarify in comments, below, thanks…
I'm looking forward to Lollipop actually… Haven't tried it yet and the update comes out next year for my Z3. Hopefully all the bugs will have been fixed.