The Dev Team has released their Redsn0w beta, dubbed Redsn0w 0.9.7b1 for iOS 4.2. We wanted to alert our readers, and at the same time provide a word of caution about the beta release.
To quote the Dev Team "This is a beta tester program. It’s not a general release! Things can go very wrong, so please don’t even consider testing if you have pictures or other media on your device that you haven’t backed up!"
For that reason we recommend you hold off until the official release, especially if you rely on an ultrasn0w carrier unlock...