Here is the full changelog..

What's New in iOS 8.1:
● This release includes new features, improvements and bug fixes, including:
● Apple Pay support for iPhone 6 and iPhone 6 Plus (U.S. only)
○ Photos includes new features, improvements and fixes
○ Adds iCloud Photo Library as a beta service
○ Adds Camera Roll album in Photos app and My Photo Stream album when iCloud Photo Library is not enabled
○ Provides alerts when running low on space before capturing Time Lapse videos
● Messages includes new features, improvements and fixes
○ Adds the ability for iPhone users to send and receive SMS and MMS text messages from their iPad and Mac
○ Resolves an issue where search would sometimes not display results
○ Fixes a bug that caused read messages to not be marked as read
○ Fixes issues with group messaging
● Resolves issues with Wi-Fi performance that could occur when connected to some base stations
● Fixes an issue that could prevent connections to Bluetooth hands-free devices
● Fixes bugs that could cause screen rotation to stop working
● Adds an option to select between 2G, 3G or LTE networks for cellular data
● Fixes an issue in Safari where videos would sometimes not play
● Adds AirDrop support for Passbook passes
● Adds an option to enable Dictation in Settings for Keyboards, separate from Siri
● Enables HealthKit apps to access data in the background
● Accessibility improvements and fixes
○ Fixes an issue that prevented Guided Access from working properly
○ Fixes a bug where VoiceOver would not work with 3rd party keyboards
○ Improves stability and audio quality when using MFi Hearing Aids with iPhone 6 and iPhone 6 Plus
○ Fixes an issue with VoiceOver where tone dialing would get stuck on a tone until dialing another number
○ Improves reliability when using handwriting, Bluetooth keyboards and Braille displays with VoiceOver
● Fixes an issue that was preventing the use of OS X Caching Server for iOS updates

Some features may not be available for all countries or all areas.

For information on the security content of this update, please visit this website:
http://support.apple.com/kb/HT1222.