stands on its own merits.
The main thing to consider here is that Windows 7 is simply Windows Vista sp2 with a few features changed around. Vista is a name that can't be marketed because of the way it was at launch, even though the now polished sp2 version of Vista is essentially what people are buying when they get Windows 7.
So is Windows 7 worth the upgrade if you are running XP? Absolutely, you're basically getting the rebadged 3 year old polished version of Vista. But for the roughly 18% of Windows users who currently have Vista with SP2, Windows 7, like PCI-E, is nothing more then a cheap marketing gimmick and could have been released to Vista owners as free service pack.
That said, like PCI-E, many people who understand will stick with Vista just as many have stuck with AGP