redsn0w has been updated to 0.9.9b3 to auto-detect iOS5 GM firmware. Remember: it’s still tethered for all devices except for iPhone 3GS with old bootrom. If you don’t use redsn0w to “Just boot” at power up, all jailbreak apps (and even some native ones like MobileSafari) will fail to launch.
If you already jailbroke the GM by pointing an older redsn0w at the beta7 IPSW, there’s no need to re-run the full jailbreak step again…just use this newer one to make the tethered boot easier
The following devices are supported under Redsn0w 0.9.9b3a.
It's important to note that this does not support unlocking your iPhone, and those requiring an unlock should stay away from iOS 5 completely until an unlock is available. Additionally, this is still a tethered jailbreak (unless you're on an older bootrom) which means you'll have to plug it into your computer each time a reboot is needed.
We'll have a full how-to up shortly to help you through the steps of jailbreaking under iOS 5 GM.
Source: iPhone Dev-Team