3.0 gigs of ram means its not running in dual channel, which kinda sucks. And the reason they didnt give you 4gb is because you're probably using the 32 bit version of vista which caps out at 3.25gb of recognized memory.
I've never bought a prebuilt computer, but I guess if you dont have the time/expertise/patience to build your own, that's a bit out of the question. It's unfortunate, because you could've gotten a much, much better computer for $1k if you had built your own. And it wouldnt be using dirt cheap/low quality parts. But again, gotta do what you gotta do. If you're happy with it, that's all that matters.