greenpois0n, the Jailbreak that supports iOS 4.2.1 untethered for iPhone, iPod touch, and ipad, has just gone into RC 6 and now also supports Apple TV untethered, and includes nitoTV. If you've been waiting to jailbreak your Apple TV (2010) but tethering was dealbreaker, now's you chance to go grab it and get your Jailbreak on.
According to @pod2g RC 6 fixes emulator issues and can be applied over RC 5 without restoring.
If you want to Jailbreak your iPhone, iPod touch, or iPad with greenpois0n, we've got your tutorials right here:
And if you want to install XBMC on your Apple TV, we've got that covered for you as well:
Link below. If you give it a try let us know how it works for you and if you need extra help check out our Apple TV Forum and Jailbreak Forum.