You can download iOS 5 now
Today's the day, and now's the time.
Same as the 1pm (EST) release dates for iOS 3 and iOS 4, iOS 5 is now available. Just open (and update if neccessary) your iTunes, then check for an iPhone software update to be prompted to download "5.0."
Apple's latest mobile software platform adds a slew of new features, including a thoroughly revamped notifications system, iMessage, deep Twitter integration, improved camera functions, and more.
The iPhone 4S launches this Friday with iOS 5 pre-installed and one exclusive feature: Siri.