Most people don't buy a Mac specifically for gaming, however that doesn't mean people don't use them for gaming. Calling MBP's internet browsing and office task machines is a bit of a stretch. Especially the 15" and 17" models, as they come with dedicated graphics and handle gaming quite well.
I've always been curious what % of the mac userbase plays games at all. Of that %, how many play games that need anything beyond a gma950? I just ask because none of my dozens of friends that use macs play games on them. Anyone have any idea of the #'s? How many units do the best selling osx video games push?