iOS 5.1 is now available for download via iTunes and brings a number of notable improvements, including Japanese language support for Siri, multiple camera enhancements as well as a fix for ongoing battery life issues on the iPhone 4/4S.

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 shows and movies on iPad optimized to sound louder and clearer
•    Podcast controls for playback speed and a 30 second rewind for iPad
•    Updated AT&T network indicator
•    Addresses bugs affecting battery life
•    Fixes an issue that occasionally caused audio to drop for outgoing calls

Battery life issues have been an ongoing problem on the iPhone 4S, with several previous updates failing to definitively address the issue.