That software is mentioned in this Wall Street Journal article about BootCamp and the Intel Macs:
http://ptech.wsj.com/archive/ptech-20060406.html
In the "side by side" table they say that Parallels runs slower than booting directly into Windows. I'd also expect that, although the author says he hasn't tried it himself. Will be interesting to see if they've solved some of the tough problems like Tim says.