RedSn0w was already able to jailbreak iOS 5.0.1 beta, but it wasn’t completely flawless like we’re used to seeing, as you had to point RedSn0w to the iOS 5.0 IPSW file. MuscleNerd has just confirmed that he has added iOS 5.0.1 beta keys to RedSn0w 0.9.9b8, this will make the jailbreak process much easier.
According to the iPhone Dev-Team’s blog:
Update #16: redsn0w version 0.9.9b8 will natively recognize the 5.0.1 beta that Apple let developers start testing this week (so you don’t have to play the “point at 5.0 IPSW” trick). Because the IPSW isn’t public, you’ll still need to provide it once to redsn0w (at whichpoint it will cache all the important pieces so you don’t need to select it again).
For those 3GS and i4 users who preserve their baseband, the Mac version can also produce the NO_BB_* custom IPSWs for 5.0.1. (But please note that ultrasn0w doesn’t get updated for betas like this.)
This is still a tethered jailbreak for all except old-bootrom 3GS users.