Apple is already pushing out the very first incremental post-iOS 11 software update out, headed to all compatible iPhones and iPads to squash some bugs and polish certain things up. iOS 11.0.1 is here, rolling out in two builds - 15A402 for non-A11 chips and 15A403 for the newest iPhones.
The update arrives with a rather non-descript changelog: bug fixes and improvements is what this one officially fixes, and nothing else is said.
However, devoted users have quickly nibbed that one out - a particular bug pertaining to the Exchange mail server has been dealt away with. Many users report that homescreen animations now feel faster and rather similar to iOS 10's animations though this could be placebo.
To get the update, just head to Settings > General > Software update, and snag it manually. If you don't see it but have been on the iOS 11 public or developer beta, make sure to delete the beta profile from your iPhone, restart the device, and then you should see the update available.