If you have been waiting for Backtrack 6 you will be surprised to know that Backtrack is now Kali Linux. Offensive security the guys behind Backtrack have rebuilt it from the ground up and have changed the name.
Some of the highlight are
Kali Linux now uses Debian instead of Ubuntu
More hardware compatibility
More easy to update.
No longer has a Pentest directory. Instead type the name of the tool any were.
You can read all about it here at their site Kali.org
Kali Linux wikipedia