Bugs aren't the exclusive province of Windows. For example, budget interfaces from M-Audio perform just as horribly on Mac OS X as they do on Windows, thanks to the badly written drivers from M-Audio. But if you're doing professional work, you won't be considering those interfaces...
In putting together a production box, especially if you're a power user looking to maximize price/performance, I don't think stability is a relevant argument anymore. I've been using Windows 7 since the beta, and it's every bit as stable as Mac OS X Snow Leopard on the same hardware. It's also a really nice OS, fast, clean and unobtrusive, intuitively layed out, etc. Apple is going to have to strive harder to differentiate themselves again - Windows 7 has really leveled the playing field.
Both operating systems are dealing with the 32 bit to 64 bit transition, somewhat awkwardly (though in totally different ways) - the main difference being that Windows forces you to decide at the point of purchase (not elegant), whereas Mac OS X handles 32/64 bits "automagically" and obscures choices from you (great for most users but also potentially frustrating for power users.)
The main thing I prefer about Mac OS X is the built in unix terminal. I like a unix-based OS. Going to the *lawl* "command line" in Windows 7 is a reminder of how pathetic MS-DOS always was, even in its heyday, and how Microsoft has completely ignored the need for a proper text interface in their OS. That's actually the thing that bugs me the most about Windows these days, which is why Mac OS X is still my production environment - I trust an OS more if it has a unix terminal at its core - and I use the terminal every day.
