Apple keeps evolving iOS 5 as they’ve just pushed beta 5 to developers. The update remains over the air, just as beta 4 worked, though some users have complained that the device requires a full wipe to allow the beta to be installed. We’re currently downloading it to our test units to confirm this, but our advice to you is that you back-up in either iTunes or iCloud before hitting the update. iTunes 10.5 was also updated to beta 5, and as expected, is not compatible with beta 4 devices, so make sure you first back-up your devices in beta 4 and then upgrade both iTunes and your iOS devices.

No significant improvements are yet mentioned, except for bug fixes and improvements. If you’re currently rocking iOS 5 beta 4, all you have to do is hit Settings/General/Software Update and then hit Download and Install. Be patient though, as in my particular case, the update only appears to be available on my iPad 2 and my iPhone 4 is still confirming that beta 4 is the newest release. The servers might be jammed, so it will take time.

Source: Developer.apple.com