Windows 7 is not anymore of a service pack to Vista than Snow Leopard is to Leopard. If you can argue that Vista is just a "fix" to the failure of Vista, then I will argue that Snow Leopard is a "fix" to the failure of Leopard.
And once again... You clearly know nothing about Microsoft's release schedule. Vista was the sole exception, coming five years after XP. Prior to this, all major Windows releases came 2-3 years later, and 7 is thus falling right back onto this schedule.
If anything, Windows 7 is removing features and bloat, not adding them. Why else would they have cut out things like Windows Calendar, Journal, Photo Gallery, etc?
They are rebranding it as a new version of Windows because there are many end-user improvements being made, just like Snow Leopard is being rebranded as a new version of Mac OS X because there are many low-level kernel improvements being made.
Perhaps Mac OS X is better than Windows, but with just barely a 10% market share, it seems that it won't be doing much "sweeping" at all.