One thing Microsoft does rather well is gets a lot of people testing software releases in extended public betas. Of course that didn't go so well for Vista, which was a mess for many people, but it seems to have gone better for Windows 7.
Apple, secretive as always, doesn't get really wide testing of new software builds, and when those updates finally get released there seems to be an ever increasing, ever louder response from customers that things aren't going swimmingly.
Snow Leopard was supposed to be a cleanup of Leopard, but it appears that some people are having lots of issues. In my own case, some fonts were pretty messed up, and Keychain was jumbled pretty badly. The fixes in both cases weren't onerous, but they were nasty enough that it made me wonder how thoroughly the release had been tested. I still don't hear new mail sounds from MobileMe, a problem that has been going on at least since Leopard was released. I'm not alone in this, but not everyone has the problem.
Most of the people I know had flawless upgrades, and of course here at TUAW we are more likely to hear about problems, which is also true of the Apple forums where people are able to report the smallest or the largest bugs.
Therefore, from my perspective it's hard to say for certain if things are slipping away from Apple quality control, but it's starting to look that way. Apple was quick to release 10.6.1, which was a good effort, but it is not quieting down the roar of users who don't think that this latest release of Snow Leopard 'just works.' What's your perception? Does Apple have some work to do?