Okay guys. Here's the deal.
I bought Call of Duty 4 for the Mac and it runs okay. I was sick of the performance issues with it, so I decided to install Windows Vista with Boot Camp and try out the Windows COD4 Demo. COD4 for Windows blew away the Mac version. I had a solid 60fps with Sync every frame on and all the fancy graphics on (ie: Shadows, Specular Map, Glow, Depth of Field) I couldn't believe it. My video card is better than I thought... It's just a crappy port by Aspyr.
So I bought the full version of COD4 for Windows and I've been loving the performance boost. Then I found this thread. Using the instructions in this thread, I was able to successfully take the PC version of the game and run it in OS X using Cider. Just so you all don't waste too much of your time, the performance is just like it is in the Aspyr version of the game. I get the same framerates I get running the Mac version as I do running the Windows version in OS X. It must just be a Mac thing. I hope Apple is able to do something in 10.5.7 or Snow Leopard to make graphics run smoother on the Mac. I know my video card is capable of handling these high end games... why can't we enjoy the same experience Windows users have? Am I supposed to spend a thousand dollars on the best graphics card to get the same performance that I can get Boot Camp with the low end card?
Anyways... in conclusion, the Windows version doesn't run any better than the Mac version in OS X. If you want the best frame rates, install Windows in Boot Camp and just reboot your computer to play. It's the only thing that works right now.