As promised by Steve Jobs on Tuesday the new iPhone 2.1 software update is available today for download.
The iPhone 2.1 software update contains many bug fixes and improvements according to Apple and you need iTunes 8 to get it.
Apple actually details the improvements made in 2.1, which makes it a significant update for your iPhone and iPhone 3G. Highlights of the iPhone 2.1 software update include Decrease in call set-up failures and dropped calls, better battery life, dramatically reduced time to backup to iTunes, and Genius playlist creation.
More details on the Apple Software Update site.