"The Dev-Team updated redsn0w to version 0.9.6b4 today, which, as detailed yesterday, will provide an untethered jailbreak of iOS 4.2.1 for iPhone 3G, older iPhone 3GS, and non-MC iPod touch 2G, and a tethered JB for the iPhone 3GS (new bootrom), iPhone 4, iPad, iPod touch 2G (MC model), iPod touch 3G and the iPod touch 4G. thanks to a combination of pwnage2 exploit, the arm7_go exploit, 24kpwn, and limera1n. For best results, upgrade to iTunes 10.1 first.
Again, it's very important to note that if you unlock, you cannot use redsn0w as it will update your baseband. So if you're an unlocker, or have a newer iDevice and would just prefer the security of an untethered JB, wait for the PwnageTool update before loading 4.2.1. Even if you are ready (like I was) to take the plunge, make sure you back up your SHSH first."
I've just done this on an iPad with the 4.2 update and it runs like a dream.
Warning 1 if you need an unlock dont update to 4.2 at the moment.
Warning 2 this is a teathered JB on the newer model iPhone and iPad, so if your idevice crashes you will have to conect to a computer to rerun the JB.
The word is that a unteathered JB is not far away.
