Well, I can tell you a thing or two about Windows as I was am a switcher myself. I had XP running well on my computer. It was pretty stable and pretty fast. The way I managed that was having a fresh install at least once a year, defragment frequently, sweeping the disk for unused files, cleaning the registry frequently, installing as little as possible, keeping drivers up to date, keeping up with ALL those (security) updates, etc etc etc.
With pretty stable I mean that it doesn't crash often, but regularly.
I have an iMac for over a year and a MacBook Pro 17" for almost a year. I have never defragmented. I have never re-installed the OS, I have been keeping up with the occasional updates. I've had my iMac turned on at home 24/7 for over 3 months while I was in Afghanistan (so that I could log on at home). And it never ever crashed during that period, or even need a restart.
Since I switched, I have experienced system freezes though, but they hardly ever happen. Do not confuse that with program freezes. I've had some programs freeze up on me regularly (mostly open source/freeware), but it never takes down the whole system.
Bottom line: Windows is blazing fast when you have a clean installation. As soon as you install a (mandatory) Virus scanner, you can feel the performance hit. After you install Office and PS, you'd barely recognize the system anymore.
OSX on the other hand still starts as fast as it did, works as fast as it did and is still as stable as it was. Although OSX isn't perfect: No way that I'm going back to Windows! It's just so much better and easier to work with! Even my wife is very happy with it!
Let's just hope they can keep it that way.
It's not fair to compare Vista installed on a monstrous (Desktop) system with a notebook (though high end amongst notebooks) that doesn't have nearly the specs that the desktop system has. Try and comparing it with a MacPro with 8 Gigs of mem and a 10k rpm disk. That would be more interesting.
