This is also the first build to be enabled over iOS 5′s built in over the air update. The over the air update is around 133MB as it’s a delta upgrade while the full download from the Dev Center is over 700MB! iOS 5 Beta 4 will need the just released iTunes 10.5 Beta 4 for syncing. To initiate the over the air update, you must be running iOS 5 beta 3. Then simply go to General > Software Update in Settings:
Update: Some are having trouble updating via software update.
Update 2: The over the air update will not work if you are jailbroken via MuscleNerd:
In order to use iOS 5 you will need to have your UDID registered. We offer UDID Activations right here!