A co-worker the other day suggested to me that Windows 7 was going to be the next Windows ME, because of the rush to market that seems to be going on. I would tend to believe the opposite; that Windows Vista is becoming the next Windows ME. However, I'm starting to become mildly skeptical of the negative press around Vista (at a time when critical mass seemed to be approaching.)
Microsoft, and thereby Vista, is a victim of its own success. Microsoft's success can be attributed to having the most accessible (in terms of purchasing and running) operating system in the PC market. Mac and Linux have passionate followings that often adopt a "common good" philosophy when it comes to necessary changes, each having their own class of power users who pull the user communities forward. Mac OS made virtually a clean break with OS X (with some legacy support), but Apple wasn't selling downgrade licenses to OS 9. Nor is Apple in the business of supporting legacy hardware indefinitely.
Windows? Windows is what you get if you buy a retail PC. Windows is the Yahoo search engine in alternate universe where Google charges per search. Windows just (sort of) works, and mostly plays ball with virtually any device manufacturer. This breed of openness through ubiquity and anarchy creates the situation where there isn't really any accountability for lack of support, yet it's somehow expected just the same.
All user environments offer their own quirks, and many proprietary and open source applications are offered to help mitigate those quirks. There's is, however, one non-quirk that I would change about Windows from a user perspective: there should be only one kernel/core dll that invokes a reboot when updated, and Windows itself should be the only thing allowed to update it. Any other changes are just fluff and a reasonably competent and/or determined user should be able to make the most of the user experience.
Some articles from the Windows XP/Vista/7 vault:
Microsoft Extends XP's stay - "Large PC Manufacturers were slated to have to stop selling Windows XP after January 31st "
Microsoft extends XP life... again
Windows XP Extensions Reflect Vista's Woes
Microsoft's Ballmer Touts Vista-To-XP Downgrade Program
Windows 7, Vista SP2 Hit Milestones