Like many I bought the beta only to discover I was running 4.2 and it wouldn’t work with the current jailbreaks.
Well greenpois0n took a number off attempts before it worked, but work it did.
The key was holding ‘menu and down arrow’, for the reboot and then straight away ‘menu and play’ until iTunes pops up. From there disconnect and run greenpois0n. It worked first time.
After, I had nitro tv on my menu. Well it actually hangs trying to find the network, press menu to get out of that screen and then re-enter network info.
From there I couldn’t instal xmbc. It just kept rebooting. I then tried ATV flash which worked, but no menu changes. After that I tried xmbc again, it worked and the additional menus appeared after reboot.
Oh you have to instal the cydia package early on, but it’s obvious. You can’t do anything but instal it.
Anyway, finally it’s working, currently I am using last fm through the tv and I am happy!