Don't Install If You're Worried About Problems
If you're having an excellent experience on iOS 9.3.4 or below, and iOS 9.3.5 fails to pique your interest, you might want to hold off for a few days or, perhaps, permanently.
iOS 9.3.5 users are complaining about battery drain, Wi-Fi issues, problems with Bluetooth, activation issues, problems with certain applications, installation problems, random reboots, and a whole lot more. The update is small but it's far from perfect.
If you're feeling comfortable with your current version of iOS you can sit back and wait for more iOS 9.3.5 feedback and potential fixes to arrive.
Remember, there is no way to downgrade to anything once you make the move to the iOS 9.3.5 update. So you'll want to be sure about the update and its performance, especially with the iOS 10 update on the way next week.
The iOS 10 release is scheduled for September 13th and some of you might want to just wait for that.