There's no definition of hipster I'd recognise that would attach itself to a Groove Armada festival. I've been a few times (last year got a freebie for the Grace Jones show cos I live near the park) and general impression is that it's relatively posh, more south and west London than east. Quite a big gay and female crowd, though, so not much "beer-fuelled testosterony" going on, certainly compared to somewhere like Wireless.
Friendly enough, but far from wild. Pretty thorough drug searches on entrance (pockets, fags etc). Also, though I've never paid, it strikes me that VFM isn't that good - last year I think was £100 for the weekend, when there's only two music stages (the second pretty minor - think Chromeo headlined it last year) and quite a few DJ tents playing fairly interchangeable sounds. (One was actually charging £2 entrance last year, which seems a pisstake, even if they had done it out like some N'Orleans bordello).
My advice would be: do you want to see the acts playing the main stage? If not, don't go. If you want a Viccy Pk dance fest, you're better off at Field Day.