XP Vs Vista
You have to step outside the box here just a little bit though and look at not just business type of networks but the general consumer, the home user as well.
There's been some problems with every OS that Microsoft has put out. Who can forget DOS6 and it's add-in features. Wiped out peoples hard drives. Or the first release of windows 95. 98 was **** until their service pack 2 and ME wasn't stable by any sense of the word.
I think Vista is stable, just bloated and requirements to use it effectively jumped, almost exponentially. Business like HP were hoping to sell more new machines and Microsoft seemed to get into bed with them and it all backfired.
Y'all present great arguments, hard to really pinpoint what went wrong. A combination of things?