I guess it is

Vista is the equivalent, at a minimum, of Windows version 12 — preceded by 1.0, 2.0, 3.0, 3.1, NT, 95, NT 4.0, 98, 2000, ME, XP. After six years of development, the longest interval between versions in the previous 22-year history of Windows, and long enough to permit Apple to bring out three new versions of Mac OS X, Vista was introduced to consumers in January 2007.

When IT professionals and consumers got a look at Vista, they all had this same question for Microsoft: That's it?

[From Windows could use a rush of fresh air - International Herald Tribune]