This is not necessarily a good thing for end users when there's a handful of different versions of Vista. Assume the average consumer in the US...that's Vista Home Basic and Home Premium and possibly Ultimate to choose from. At first glance do you know what the differences are? Or whether or not you need an upgrade or full version? (Let's not even get into the other versions of Vista, System Builder/OEM, EU versions, Windows Server et cetera.)
Compare with OS X (ignoring OS X Server). There are only two versions, period: OS X and OS X Family Pack. How obvious is it what the difference is between the two? Very. You just count the number of computers in your household you want to install OS X on, and buy accordingly. No upgrade/full version worries, no "what does this have over the other one?" worries, no buying something you don't need...
Sure, OS X doesn't come in so many "flexible" configurations as Vista does, but the thing about it is that you could just do that on your own if it meant so much, and otherwise you get a default config that works for most people.