iOS 5.1 is release and can be updated either by connecting your phone via USB or over the air.
This update contains improvements and bug fixes, including:
Japanese language support for Siri (availability may be limited during initial rollout)
Photos can now be deleted from Photo Stream
Camera shortcut now always visible on Lock Screen for iPhone 4S, iPhone 4, iPhone 3GS and iPod touch (4th generation)
Camera face detection now highlights all detected faces
Redesigned Camera app for iPad
Genius Mixes and Genius playlists for iTunes Match subscribers
Audio for TV programmes and films on iPad optimised to sound louder and clearer
Podcast controls for playback speed and a 30-second rewind for iPad
Addresses bugs affecting battery life
Fixes an issue that occasionally caused audio to drop for outgoing calls
For information on the security content of this update, please visit this website:
http://support.apple.com/kb/HT1222