It's been said before, the gaming landscape in Mac is just sad. They do get some new-ish games but they miss a LOT of games that never make it, and those that do are generally at least 8 to 12 months late. By the time it comes on the Mac it's an old game on PC, and almost always runs slower, even if you have the very top of the line Mac dual G5.
That said, OS X is indeed years ahead from Windows at nearly everything. Beautiful, super-stable, solid, great support, smart, and there's a ton of brilliant software. But it's also a very limiting environment. You either do it the Mac way or you're stuck. You better like iTunes and iPod and iPhoto because if you don't, you're basically screwed, doomed to living in the fringes of a fringe community. On PC you have an overwhelming amount of choice.
For me personally, the biggest problem is speed. Even the "World's fastest supercomputer" (haha), the dual 2Ghz G5 is not exactly a speed demon compared with an Intel or AMD-based workstation for less then half the price. It's MUCH worse with the notebooks. Compare the processing speed of any Sager or fast Centrino against the fastest Powerbook you can find and your image of these beatiful notebooks will change... I know because I own one myself, in addition to a couple of Macs, plus in my work environment about 50% of people use Macs. Don't trust anytning Apple says or benchmarks, they lie as much as any other company would dare to. Just try it yourself. If it's as fast as you need it, then buy it, you will like it.
My other personal problem with the Mac is Mac users themselves. They are very often egocentric, elitist zealots with a superiority complex, and proud of it. Too close to a cult for my taste. And that's always bad, even if they don't realize it. Everytime I follow a "Mac vs PC" conversation and the Mac zealots come in with their usual ignorant rants about how Apple invented everything, Microsoft is an evil thief, anybody who doesn't use a Mac is a masochist retard, etc., it makes me think twice before powering up my G5 and having to share something with them.
Today, I use my PCs all day, every day, and my Macs every once in a while to check out a new program or when I want a break from Windows.
Microsoft, please hurry up with Longhorn, I don't want to be assimilated by the iBorg.