Apple has finally unleashed the iPhone 2.1 firmware to the masses.
- Decrease in call set-up failures and dropped calls
- Significantly better battery life for most users
- Dramatically reduced time to backup to iTunes
- Improved email reliability, notably fetching email from POP and Exchange accounts
- Faster installation of 3rd party applications
- Fixed bugs causing hangs and crashes for users with lots of third party applications
- Improved performance in text messaging
- Faster loading and searching of contacts
- Improved accuracy of the 3G signal strength display
- Repeat alert up to two additional times for incoming text messages
- Option to wipe data after ten failed passcode attempts
- Genius playlist creation
So you can check this site for instructions in upgrading.