I was pretty excited by the news you just released MI for Mac and, even if I've already played all the episodes on Boot Camp, I re-downloaded everything just to be able to play whenever I want without the need to reboot.
Although I was disappointed by how slow the game runs under Mac Os X, I'm aware I own a white MacBook 2.15ghz, 4gb ram, with a really slow graphic card (Intel GMA 950) but I had to lower the detail level to 1 and resolution to 640x480 to be barely able to play the game, and when I say barely it means it probably runs at 10-15 fps.
On the other side I was able to play MI with detail set to 3 and resolution set to 1280x800 under Boot Camp, in a pretty good way, probably around 20/25 fps.
I'm not complaining at all, I just wanted to give you my feedback and experience, maybe it's just a matter of optimization but a so big difference left me doubtful.
that's all, and as always keep up with the great work you're doing, I'll keep supporting you! :-)