Keep making excuses. Microsoft's last true retail success in operating systems was Windows 95. Windows 98 was a genuine improvement, but it was not the retail success that Win 95 was. We all know that the follow-up Windows Me was an unmitigated disaster. In this sense, the disaster that is Vista is not new.
The larger issue is that for more than a decade now, Microsoft has over-promised and under-produced in the OS market. Go back to Windows 95. Microsoft called it Windows without DOS. The facts were the exact opposite. Windows 95 was based on MS-DOS and required it to operate. As I said above, Windows 98 was a genuine improvement in Microsoft's DOS-based OS. With Windows Me, Microsoft discovered that you can't push a rope.
Windows 2000 promised to replace the DOS-based and NT-based branches of Windows with a single unified branch. Didn't happen. Windows XP was what Windows 2000 was supposed to be. However, it was susceptible to the most dangerous computer malware in history. Without question, Win XP has improved since its introduction. However, it is amusing that so many Windows users now hang onto XP when presented with the prospect of Vista.
Now we hear that Windows 7 will be The Promised Land and Windows users can put the Vista nightmare behind them. We have heard it all before. It wasn't true then. It isn't true now.
Look, I'm no MS apologist. I work with it every day, and I'm painfully aware of the problems. There is a reason why 2 of my 3 personally owned machines run OSX. I completely agree that MS has repeatedly over promised things. My point is that Vista is not nearly as bad as the public perception. Heck, Vista is actually much more secure than XP, if for no other reason that you can actually do stuff in it without being an administrator. That fact alone is a huge improvement over XP. (End users turning off UAC and running as admin is a different issue). Notice that until the Conficker worm, Vista had not been subject to the huge self installing/propagating worms that XP was. Another point on the Me vs. Vista thing is that ME really was a disaster, whereas Vista is perceived to be a disaster.
The problem is that Microsoft had backed themselves into a corner. They really need to do what Apple did with OSX: Completely scrap the old OS, and start over. They tried doing that in the early stages of Longhorn/Vista, and it failed because of backward compatibility. Microsoft's enterprise customers won't put up with something that breaks compatibility, even if it is much better in other respects. MS could build something much more stable and secure, but they won't because they would tick off too many customers. Thus, they have to make sure that their OS still works with ancient versions of Office, custom DOS based apps, and other apps that haven't been updated since the NT days, simply because their customers refuse to upgrade.
Is Windows 7 the promised land? Probably not, but is is an improvement over XP and Vista. If they can actually get it to market without adding on a bunch of useless bloat, it may actually be pretty good. The question is if it is too little, too late.