The biggest addition in terms of new features in iOS 11.2 is Apple Pay Cash, a feature that allows you to send, request, and receive money from friends and family with Apple Pay using Messages or Siri.
This feature is US-only at present, but expect it to roll out worldwide over the coming months.
As for other fixes and tweaks, here's what Apple lists in the release notes:
Introduces three new Live wallpapers for iPhone X
Improves video camera stabilization
Adds support in Podcasts to automatically advance to the next episode from the same show
Adds support in HealthKit for downhill snow sports distance as a data type
Fixes an issue that could cause Mail to appear to be checking for new messages even when a download is complete
Fixes an issue that could cause cleared Mail notifications from Exchange accounts to reappear
Improves stability in Calendar
Resolves an issue where Settings could open to a blank screen
Fixes an issue that could prevent swiping to Today View or Camera from the Lock Screen
Addresses an issue that could prevent Music controls from displaying on the Lock Screen
Fixes an issue that could cause app icons to be arranged incorrectly on the Home Screen
Addresses an issue that could prevent users from deleting recent photos when iCloud storage is exceeded
Addresses an issue where Find My iPhone sometimes wouldn't display a map
Fixes an issue in Messages where the keyboard could overlap the most recent message
Fixes an issue in Calculator where typing numbers rapidly could lead to incorrect results
Addressed an issue where the keyboard could respond slowly
Adds support for real-time text (RTT) phone calls for the deaf and hard of hearing
Improves VoiceOver stability in Messages, Settings, App Store, and Music
Resolves an issue that prevented VoiceOver from announcing incoming Notifications
On top of this, Apple has also tweaked how the Wi-Fi and Bluetooth on/off buttons in Control Center work (detailed here - don't get too excited by this, I think it's an ugly solution). Apple has also used this update to fix a bug where notifications generated by apps after December 2 caused iPhones, iPads, and iPod touch devices to crash.