I just installed iOS6 on my iPhone4 with 8GB and the features that appear to be included are:
Perhaps others I did not recognize or may be added in later iOS updates.
- Dedicated signatures for each email account
- Facebook integration
- Offline Reading List
- Passbook (the only new icon on the phone)
- Shared Photo Stream
- VIP Inbox
- Do Not Disturb
- HDR Photo - Keep Normal Photo
Perhaps others I did not recognize or may be added in later iOS updates.
- I love the dedicated signatures for my business, teaching and personal accounts because it allow me to add specific phone numbers, websites, etc to each signature.
- Offline Reading List is also very nice to have
- Passbook appears to be vendor specific so American Airlines, Lufthansa and United are the only ones listed for boarding pass integration, There's Target and Sephora, TicketMaster, Walgreens, MLB and a few others so far.