I have been playing around with Parrallels Desktop For Mac on a MacBook. So far it has been pretty cool.
In the past if you wanted to run Windows on a Mac you had to use VirtualPC and it had to emulate the intel processor and using it sucked. The new macs have an intel processor so there is no need to emulate. Apple supports dual booting with BootCamp, but I need to use both at the same time, and having to reboot to do something doesn't sound like fun.

The first thing I have noticed is that it likes RAM, lots of it. It's pretty basic: two operating systems need twice(or more) the RAM. So you have the MacOS and it really likes at least 512MB to do its usual things. Then you run Parallels and it loads the multi-gigabyte hard drive file. Then Parallels lets you adjust the amount of RAM that you want to give each virtual OS and it defaults to about 500MB. When I did this the computer freaked out. The CPUS were at about 15 percent each, but the computer only has 1GB of RAM and it was paging like crazy. I had to scale it back to about 300 to get the Mac useable. Then you get to feel like you are using Windows XP with 256MB of RAM!!!!

There is also a < a href="http://www.multisolar.com/software/PDTweaker/" target=_blank>hack that adjusts some things and makes it a bit faster. Hopefully this will be integrated into a newer version of Parallels.