Right after update to 11.0.0 (and all further updates up to 11.0.3) my iPhone SE experience became quite painful. I have two different symptoms:
Many apps are freezing for several seconds at random moments often.
In few days after iPhone restart I can't hear my callers (and vice versa), when I restart my phone the problem is fixed for next few days.
It's a 1 year old 64 GB iPhone SE MLM72RU/A which worked perfectly 1 month ago.
problems with iPhone SE on 11.0: apps freezing and voice call pr
I am using the same model, and for me, iOS 11 has been working quite nicely. One suspects a hardware issue.
Note that I do weekly re-boot the SE from a dead stop, just to keep things clean.