I've got a praxis and a proton and both are pretty sweet. the out of the box range is ridiculous, pretty accurate too. I've been considering buying a nitron but it's had pretty bad reviews, then again holding one yesterday it felt pretty sweet (out of batteries). I might wait till the value pack with the extra tube mag turns up at the kmart near me.
As for dart blaster internals in a vortex, I wouldn't bother, they still fire a projectile, and definitely out-perform stock dart blasters. But that's just me, just because it's a flat projectile and not a tube shape doesn't really put me off.
One thing I'd like to see though is more different designs, rather than designs that sort of mimic N-strike (nitron/stampede, proton/nitfinder). oh, and a 100 disc ammo box. I lose them was too easily.