I'm a big fan of OS X, but the fact is there are some programs that run better in Windows, namely games. Surely there are other examples too, like Microsoft Office (I find it appalling on Mac OS X as well as Windows, but what can you do), or other "work" programs, however I'm mostly familiar with video games.
In my opinion, suggesting people to just abandon their macs and buy a windows machine is ridiculous. I bought a mac because I VERY much prefer the OS X environment. I absolutely hate using Windows. If I have to I will, but it is not nearly as intuitive and pleasant for me as using my Macbook.
Having both operating systems on the same computer is convenient, and I switch back and forth in around a minute or two. If that's too much of an inconvenience for you, then that's your issue.
On the issue of compatibility and performance..
I'm on a 1st Gen 2006 Macbook with Leopard installed. Windows 7 runs amazingly on it. Fact of the matter is, Windows crashes. A lot. When Apple users, who are accustomed to RARELY ever getting crashes, first start using Windows and notice even a couple crashes they start pointing fingers and making bold claims.
Compared to other computers I've used, running Windows 7 on my Macbook has been a wonderful experience. Don't get me wrong, I very much prefer OS X, however, compared to other Windows computers, I'm not plagued with constant crashes, slow down, or driver errors when running off my Macbook.
Of course, drivers can be a factor explaining the amount of naysayers. Perhaps I have lucked out and Apple has made great drivers for my specific Macbook (perhaps because it is a simpler computer?); I just want to point out that even older machines can run it very well. It isn't an issue with "age" or "specs," it may just be an issue with drivers or misconceptions of how well Windows runs in the first place.
Anyway, I'm off to play Oblivion on my macbook!