i’ve updated my apple tv to 4.2.2 and jailbreaked is successfully with seas0npass.
after installing atv flash beta 5 and xbmc (version 10.0-8) i am missing some addons in xbmc 
for example there are only 3 different skins available 
10.0-8 is the latest nightly working apparently. 10.0-9 seems to have a few issues
http://passion-xbmc.org/addons/?Page=View&ID=plugin.program.repo.installer
List of Unofficial Add-on Repositories
Installing nightlies ) Log into you AppleTV via ssh:
$ ssh root@<your ATV2 IP address>
root@<your ATV2 IP address>'s password: ‘‘enter your password here, it should be “alpine” if you haven’t changed it’’
To Add the missing repository and make update on the AppleTV:
echo "deb <a href="http://apt.saurik.com/" target="_blank">http://apt.saurik.com/</a> tangelo-3.7 main">/etc/apt/sources.list.d/saurik.list
apt-get update
$ apt-get -f install
To Install the latest nightly build from xbmc:
a - wget <a href="http://hadm.net/xbmc/latest_atv2.deb">http://hadm.net/xbmc/latest_atv2.deb</a><a href="http://hadm.net/%7Ekeith/xbmc_atv2/latest_atv2.deb" target="_blank"></a>
(then hit enter and wait until its done downloading)
b - dpkg -i latest_atv2.deb
(then hit enter and wait until its done)
4) Just to make sure that all dependencies have been installed properly:
$ apt-get -f install
thanks a lot 8)
i’m just a little bit sad because updating via atvflash don´t work… is it so complicated to offer the actual version of xbmc?!
Actually, since both fireCore and XBMC are in beta and developed independantly of each other it is rather difficult to do that. On the bright side there is an add-on for XBMC that will list the latest stable or nightlies in the GUI. XBMC Builds Repository has a configuration to allow you to save the download to the local folder and execute.