No issues on my old Pixel 3.
Some big changes for me to get my simple head around though. E.g. I used the ‘up swipe’ to recall recent apps all the time on A11. That’s changed now in A12 so that you need a much longer / taller swipe to do the same.
Driving me mad and hadn’t realised how much I used that action.
But aside from my own inability to change with the times, the rest of the OS is working fine on what’s an old phone.
I’ve also ordered a 6 (Pro). My poor old 3 was in my pocket during a significant off and the glass on the back is shattered, with lumps falling off daily. I just hope it lasts til the end of next week.
Max trade in on the 3 (with no issues) was GBP50 from Google. Seemed a bit tight against a GBP849 phone, albeit with GBP300 headphones thrown in.
Anyway, A12 seems stable and worth experimenting with. But there was not much wrong (if anything) with A11.