If all the new emoji weren't enough of a reason for you to upgrade to iOS 10.2, the security updates added to the release should really push you over the edge.
Apple's security updates page outlines the changes, which will work on the iPhone 5 and later, iPad 4th generation and later and iPod touch 6th generation or later.
One of the security issues the update fixes is the a weird unlock trick that went viral on YouTube back in November. By going through a series of convoluted steps, users were able to access photos and contacts from the lock screen -- without actually unlocking the phone.
That bug is now fixed, along with a few other security bugs that could have allowed someone with physical access to your phone to unlock it. Apple didn't detail exactly what these exploits were, but the bugs are patched now.
As always, this is a good reminder to update your software to the latest version. With so many people trying to crack the software in our phones and computers, staying up to date is one of the best ways to protect yourself.