VirtualBox is free so the downside to trying it is just your time. I did, and stayed with it. I primarily run XP but I did play with a couple of Linux flavors on it as well. 

Its seamless mode works well, showing only the application's windows on your OS X desktop among whatever other OS X stuff is there. I point my few remaining Windows apps to shared folders on the OS X file system which means I don't have to backup the Windows VDisk very often; my data is safely included in my OS X backup scheme.