I have an bootcamped iMac, which isnt a laptop but applestuff none the less. I have 2.66GHz Intel Core Duo or something like that CPU, 2 GB ram, ATI Mobility Radeon 2600 XT gfx card. TF2 runs decently enough for me (30-60fps) at 1680x1050 reso with full settings apart from no AA and Anistrophic Filtering set to 2x. L4D pretty much the same, except for that I dont run any AF on that. L4D2 same as L4D1. When it comes to photoshopping it runs just fine, same with modelling and all kinds of other stuff.
I can run newest games and even the god of unoptimizedness: GTA4, but that requires lowering the resolution to something like 1280x768 tho. Personally I dont get why you want a mac if youre planning to use windows on it, since I only ever use the mac-side is when I fuck up (kill windows) and need to find help for my problem (but usually end up reinstalling).