Been running iOS 11 on my 7 plus since Beta 5 and it's been very smooth. I get a couple minor hiccups here and there and a few resprings but that's about it.
I was getting double messages, first it would come as an iMessage then it would come as a text. Stopped doing that on it's own. Weird. Other than that no issues.
3D touch animations are stuttering on my 7 Plus, some lags, re-opening safari drops frames as well sometimes...
These issues started in early betas and have not been fixed in the final release...