Granted, Vista wasn't as bad at launch as XP was at launch.
-When XP launched, we had recently been treated to ME, the worst piece of shit MS has ever come up with.
-Prior to that, 2K worked badly enough that scores of people were still on 98. (This doesn't mean 2k was a bad OS, per se-just that it was a workstation OS, although I personally don't like it and it shows, even though XP was built off of it.)
-The difference in functionality between 98 and XP was miles.
-When Vista launched, XP was stable and everyone loved it.
-Vista was in betas/development for quite a bit longer than XP was, with a much larger userbase involved in it.
-The launch looked worse than it was, and the whole 16GB installation thing and the appearance of eating up all your RAM didn't help either.
-The 95 different flavors wasn't a good move. Okay, so it was only four. But one of them's useless (though people will still choose it anyway!), and XP only had 2 choices, where the choice didn't really matter. (XP Media Center Edition was introduced much later, and to my knowledge has only been available in a preinstalled state anyway. Besides, it's basically Home with more toys.)
-Personal pet peeve: There's still a 32-bit Vista. A lot of us, as it turns out, were hoping MS would wise up and go full bore with 64-bit.
Conclusion: Vista launch needed to be impressive and was disappointing instead, which is why everyone looks down on it, regardless of how good it may have been and regardless of how good SP1 may have made it.
This has been your offtopic for the day; tune in next time for an Apple rant (or whatever else comes up).