Don't Install iOS 10.2.1 If You're Worried About Problems
If you're having an excellent experience on iOS 10.2 or below, and iOS 10.2.1 fails to excite you, consider holding out.
iOS 10.2.1 users are already complaining about Wi-Fi issues, various issues with Bluetooth, activation issues, problems with various third-party applications, installation problems, UI lag, random reboots, and battery drain issues.
To make matters worse, the now infamous "30% battery" issue appears to be unresolved in the iOS 10.2.1 update.
If you're feeling comfortable with your current version of iOS you might think about waiting for the next versions of iOS 10 to arrive.
Remember, there is no way to downgrade to iOS 10.1.1 or iOS 9 so you'll want to be sure about your move to iOS 10.2.1. Once you make the move to iOS 10.2.1, your only option is to stick it out or downgrade to iOS 10.2.
It's unclear when Apple plans to release its next iOS 10 update but it could be a few weeks before we see something new.