Don't Install If You're Worried About Other Problems
If you're having a flawless experience on your current version of iOS and you're concerned about iOS 11.3.1 problems, it might be a good idea to wait a few days before committing.
iOS 11.3.1 is a bug fix update, but its brought its own collection of issues to iPhone, iPad, and iPod touch owners.
The current list of iOS 11.3.1 problems includes weird battery drain, issues with first and third-party applications, finicky Bluetooth, problems with Wi-Fi and cellular data, installation issues, lag, issues with smart punctuation, random reboots, and missing battery indicators.
If you're feeling leery, you might want to wait for Apple's next iOS 11 update to emerge. Apple's confirmed a iOS 11.4 update and it should arrive in a few weeks.
There's currently no way to downgrade so you'll want to be confident in your move to iOS 11.3.1.