$90 is about as cheap as you'll find for a complete rig, paintball or no (CO2 cylinder is extra).
The needle valves on all of the cheapo models are pretty much identical (crap). 50 psi preset working pressure isn't horrible, but a higher pressure will make it more difficult for very precise changes without a good needle valve, which none of the ones that have been mentioned, have.
The premium has an adjustable working pressure.
I wouldn't stress too much about any of this. This is all lower-end stuff we're talking about, and you *will* upgrade at some point, depending on your financial situation and frustration tolerance. With the premium on evilbay i mentioned, you get a bubble counter/diffuser (both functional but crap). You'll still need a $15 adapter to use with paintball, though.
I don't think the mini comes with anything, but I could be wrong. Whatever you decide, make sure that you have the correct adapter (the mini comes with one), a bubble counter, diffuser, tubing, and at least one check valve. Those will add on to your purchase. Oh, and you'll need to be willing to run out to get a refill on the tank (you'll have at least a few days as pressure starts to drop) or get a backup can. My guess is a pb can on a 10g tank will last 3-4 weeks, give or take a bit.