Lots of UI slight delays and glitches. Not really major, but it looks scrappy at times.
And I'm on a 6S. These phones should be powerful enough now to handle OS changes for a long time. Apple can't keep claiming each new phone is the fastest thing the world's ever seen them 5 years later they can't handle a pretty much identical OS.
You know what mate, now you mention it, since 11.0.1 I have noticed slight UI delays. Tapping home and it struggles to minimise, the animation is sluggish at times.
That is on a brand new 8 Plus as well, so it is nothing to do with your phone.