Today, iOS 5 became available for the iPhone 3GS, iPhone 4, iPads 1 and 2, and the 3rd and 4th generation iPod Touch models. Besides there being some 200 new features, there are several changes and improvements to VoiceOver. As usual, the Maccessibility network has done a tremendous job reviewing what is new in VoiceOver. You can read all about it
here.
Note that you must have iTunes 10.5 to be able to update to iOS 5 on your iOS device. Additionally, Mac OS 10.7.2 with iCloud support is also available as a software update.