Backtrack five has been released today, has some big improvements from 4. However websites a tad slow due to high demand.
http://www.backtrack-linux.org/
http://www.backtrack-linux.org/
Will have a play with this later in the week, will be using it in my new job quite a bit
How are others running it, off a USB, hard drive install or through a VM? I'll be doing the latter.