I should add... I'm now using MC through Parallels Desktop 7 on a variety of different Macs and it works absolutely GREAT. I'm currently using it on:
1. My recent-model (Sandy Bridge) 15" Macbook Pro.
2. A current gen (Sandy Bridge) low-end Mac Mini with no upgrades except 4GB of RAM (added aftermarket because I'm cheap)
3. A first-gen Mac Pro (1,1, the very first Intel Mac Pro ever released), that has GOBS of RAM but not too much else special.
4. A Mac Pro 4,1 which is a Nehalem, dual-CPU, quad core system (so 8 cores total) with 8GB of RAM
In all cases except #3 above, I'm running Windows 7 x64 inside the Parallels VM, while on the old MacPro (#3) I'm using Windows 7 32bit instead. On the Mac Pros and Macbook Pro, I have Windows installed in Boot Camp (where you can reboot the whole computer to Windows), and then the Boot Camp partition set up in Parallels. On the Mini, I just installed Windows 7 directly in Parallels without setting up Boot Camp first.
It works basically PERFECTLY in all cases.
The one thing that makes a big difference is RAM. Since Parallels is essentially running a whole second operating system on your computer side-by-side with OSX, it "separates out" part of the RAM and uses it for Windows. The only performance problems I see are with my Mac Mini because it only has 4GB total. I set Parallels up on that system to use 1.5GB of RAM for itself, and leave the rest for OSX. That's probably the minimum that is pleasant, and Windows really wants more than 1.5GB of RAM. I'm planning to upgrade the Mac Mini to 8GB as soon as I have the time. Luckily, RAM is stupidly cheap right now (unless you buy it from Apple). GSkill makes really nice Mac-certified RAM that works great and is available on Newegg.
One other tip? Windows is on sale right now for the holidays all over the place. Newegg and Amazon both have an OEM copy of Windows 7 64bit for $99 currently. An OEM copy will work fine for this.