I signed up and downloaded the Vista Beta 2 ISO and was greeted with the popular 80070241 error. Supposedly I just need to re-download a non-corrupt ISO... Perhaps, if time allows. In the meantime, there's plenty of other people having their own Vista issues.
Edit 7.4.06 : Turns out it was a bad download. I redownloaded and reburned the ISO and Vista installed without issue.