Is there a decent used bike market in your area? At that price point (~$400-450), you might be a little better off with an older hardtail, assuming you can do a little wrenching yourself. Last winter I picked up a cosmetically rough but very sweet 1999 XTR/XT Voodoo Bizango (fully rigid) with nice Mavic wheels for $380 or so....
Weak points with all the bikes bikes are the Dart fork, Tektro brakes, and off-brand wheels. Good V-brakes will probably be less of a pain to keep adjusted than low-end mechanical discs. Drivetrain isn't bad at all (anything Deore or LX or higher will be fine, generally). I don't think they're bad deals at all -- it's just difficult to find a really off-road worthy bike at that price point. You'll probably go through a bit of a cycle of breaking and replacing some of the components, although there's nothing wrong with upgrading as you go. Good luck!