Funny. I sit here reading this nonsense and feel compelled to reply. For one thing, I'm running Windows 7 on a machine that Vista could not run. In fact, the machine is old enough that it is no longer supported by it's manufacturer. Windows 7 Pre-Alpha (M3) runs really well on it. So well in fact, that this machine is now my main home machine. Now, the technical details of why Windows 7 can run so well on lesser hardware are based on many changes to the core system (which is fundamentally Vista). There is no other explanation. I see what I see and I like what I see.
All of this said, Windows Vista SP1 blazes on my more powerful machine (another laptop primarily used by my girlfriend) and is highly reliable, stable, boots fast, resumes incredibly fast. Basically, it's rock solid.
Windows 7 is not Windows Vista, but it is based on the same core OS (though make no mistake, the Windows 7 core has been improved through many learnings from Vista telemetry data and a great deal of customer feedback as well as many engineering innovations concocted by Windows engineers that did not arise during Vista development because, well, engineering innovation takes time and operating systems do not evolve in a vacuum - lessens learned from Vista in the real world helped stimulate new ideas that find their way into next iterations of Windows...).
Windows 2000 was the first iteration of a client OS based on NT. Windows XP was the next (and more user friendly) incarnation of the OS introduced in Windows 2000. Windows Vista is a very different OS than XP, it's an evolutionary step, as opposed to a modest step (this is the basis of many of the application compatibility problems first encountered when Vista shipped,).
In much the same way as Windows 2000 grew into Windows XP, Windows Vista will form the basis of Windows 7. This does not mean that Windows 7 is just Vista with a new shell. That's a very ignorant way to think about it and it's completely untrue to boot! But don't take my word for it. Go read (and understand) the
Engineering Windows 7 blog and watch the Mark Russinovich interview,
Inside Windows 7 (make sure you actually listen to what he says).
C