My brother tried it, and didnt like it... I ant had a chance yet as I havent got a hardrive free to put it on. When I get a new drive I will have a play then.
We downloaded the Longhorn_4051_PDC_WINBETA.iso
Then I had to add some boot information into the ISO using UltraISO
Then change some other files in the iso, so that you have a key that works.
Then install and do some more stuff, which im not sure on yet, having not installed it yet.
I've played with it in VMWare. It's very much a pre-alpha build, very slow, very sluggish, very prone to die.
At the moment it's basically XP with a new explorer and the beginging of WinFS.
You definitely won't be running it on a BP6 methinks, certainly at the moment you wouldn't want less than a gig of RAM for it.