Now, Windows is playing catch-up. They need not only to fix Vista but to add improvements. The ones they are adding still mostly fall into the Leopard blanket of feature, with the exception of the patently bizarre "half-window" feature. Apple, meanwhile, is calling Snow Leopard a speed tweak: they're reducing filesize, adding Exchange support, and improving their Quicktime codecs for native filetype support. In other words, they're closing the window and removing vulnerabilities. Everybody thinks Apple has the superior featureset, and if they're also faster and sturdier and have business support, then they have a legitimate chance of getting the vast upper hand here.
I think Microsoft is learning from their mistakes, but they're learning slowly. It'll take them a long time to clean out the muckiness of their operating system and create something as minimal as OS X. And, from what I've seen of Windows 7, they're still not going at it the right way.