The vita didn't sell "well" in terms of over all. only about 60% of launch stocks were sold, which is not actually a good number. HOWEVER, fun fact. 3G ones are over-stocked while the Wifi ones were sold out at most metropolitan cities in Japan. The 3G used one sells about the same price as a used wifi one, with the simcard included.
Long story short, no one cares about 3G....it could be due to the shitty Data Plan, but it could also be the fact that the 3G is targeted at the wrong consumers, majority of the gamers don't care to play over data-network when they are on the go (keep in mind, Japan market is not the same as Western)
Basically, Vita isn't a success but it isn't a flop either, at least by first week data. Currently, it's reputation is about the same as what 3DS was when it first came out, however, 3DS is getting more attention at the moment, especially due to Monster Hunter "4"
As for me, I am happy with my Vita and would recommend it. So far I have Army Corpse of Hell, Shinobido 2, Uncharted, Katamari, Ridge Racer. I'm a Ridge Racer fan and especially Sampling Masters (Mega and Aya mainly) fan so I am happy with Ridge Racer as is (2980yen + 1000yen dlc when it's ready). Shinobido 2 is more like a ps2 game but it is fun if you like Tenchu or part 1 of Shinobido, Army Corpse of Hell...it's like Pikmin that's more centered towards action, Uncharted is Uncharted. Katamari...I didn't like as much as I thought I would.
I believe the issue with the 3G was that it was pretty much useless (no online gaming, just downloading). No need to have 3G when people have smartphones for social networking/web browsing.
However, I might pick one up anyway... we'll see. How's the memory card usage? I'd imagine that would be an impediment to sales