Well, I guess this is a closed issue really, but I'd like to chime on on the what I optimistically regard as the reasoning behind the sluggish - and even buggy - performance of MacOS X up to now. The argument I've heard most often is that they needed to have a stable release first and then begin paring it down and optimizing. As a developer I've tended to do the same thing, taking optimization as the icing on the cake, so to speak.
I'd like to pretend it has absolutely nothing to do with marketing, but I'm willing to admit that Apple felt they needed to get MacOS X out the door before it was entirely perfect. The Cube was a marketing disaster after all!
But I wouldn't have traded my 4 months of MacOS X experience for 4 months of playing with Conflict Catcher every other day. I've done about 5 installs of MacOS X on my home and work machines combined, the last time so I could move to a larger partition. But it got easier every time, thanks in part to Apple's diligence in providing 10 combined 10.0.0 - 10.0.4 and other updates as disk images.
Of course Apple was counting on my loyalty, and they've kept it despite their flaws, such as a dearth of update documentation. They counted on the fact that most "early adopters" would be brave long-time Mac gurus. Looking around the forums that have existed for Apple products on UseNet, MacFixit, here, and elsewhere for 20 years I find an amazing user base willing to help each other out of any jam. Apple surely counted on this too.
I guess the most true and positive thing you can say about MacOS X at this moment is It's only going to get better!