I just checked my iPhone and it seems that iOS 5.1 is available for download.
Whole raft of improvements are on offer:
- Japanese language Siri
- Photos can now be deleted from the Photo stream in iCloud
- Camera shortcut always visible in lock screen
- Camera face detection
- Better camera app for iPad
- Improved Mixes and Genius playlists
- Audio for TV shows louder and clearer
- Podcast controls for playback and 30 sec rewind
- Updated AT&T network indicator
- Addresses battery life bugs
- Fixes a bug that causes audio on outgoing calls to drop
You can download the update via iTunes of if you have iOS 5.0 installed OTA (Over The Air) by going Settings > General > Software Update.
I've installed it on my iPhone 4 and iPad with no problems at all. I'll get back to you with some first impressions later.