Apple has released iOS 5 beta 5 for iPhone, iPad, and iPod touch to developers. Like the previous update, iOS 5 is being offered over-the-air (OTA) so tap Settings on your device, go to General, and hit Software Update, and watch it do its magic.
As mentioned in the comments, Apple is officially recommending you wipe your device before updating:
To install iOS 5 beta 5 using over the air software update, you must first erase all content and settings on your device by choosing Settings > General > Reset > Erase All Content and Settings. Over the air software update can be initiated on devices running iOS 5 beta 3 and later by choosing Settings > General > Software Update.
Be sure to backup your devices using iTunes 10.5 beta 4 or through iCloud backup prior to installing iOS 5 beta 5. After installing iOS 5 beta 5, you can restore your device using either iTunes 10.5 beta 5 or through your iCloud backup.
We've had a couple of successful updates without wiping, however. Apple may just want to have devices returned to a known state prior to update as a best practice. Ignore it at your own risk.
No word on changes yet. More as this develops.