Doesn’t running Windows alongside OS X use up, like, a ton of memory?
It’s not that big an issue.
First of all, memory is dirt cheap these days, and everyone running a modern OS X machine should have at least 2GB. With 2GB, I can run Parallels and all my Mac stuff with no problems. If I noticed that my performance was suffering, and I had to do this all the time, I would just get more memory. The only Apple machines that have low-memory issues are laptops, which max out at 4GB these days.