I work in the Office of Technology at college, and we deal a decent amount with Windows on Mac issues. All the long term guys in the office swear by VMware over Parallels. So much so that if a uses requests for us to install Parallels, we try to suggest VMware to them.
And I've recently put XP and 7 on my MacBook Pro using VMware, it was a dream, installed without issue and they run great. Not to mention the neat stuff you can do since I last used virtualization software. Running MS OneNote inside of VMware, but making it look and act as though it were a native OS X program is great!