Internal hubs should decrease the frequency of your maintenance over a derailleur system (ie, stuff doesn't break as often), but they are much more complicated when something does go wrong. This includes changing a tire, because you have to wrestle the shift cable off before removing the rear wheel. If you park outdoors during the day (or at night) in all conditions, IGH is probably for you. If you store your bike inside, I would go with derailleurs. If you go IGH, check out the Trek Soho DLX. Disk brakes, Belt Drive, 8sp IGH... pretty much maintenance free until something breaks (no "tuning" or lubing stuff constantly).

If you go derailleurs, I would steer away from the commuting category and look purely at rigid mtb's and sport hybrids. Something like a fully rigid Niner with slicks and set up as a 1x9 drivetrain (or however many rear gears you want) would be my dream commuter for this area. Might be doable in your price range if you shop for your parts right (and do the labor putting it together yourself).

As for the hybrids, every major brand makes them, and there aren't a lot of differences between them. They are probably lighter than a rigid MTB and a little more efficient on road. Some err on the cheaper side, some give you some better "other parts" (saddle, tires, etc) at a little more cost, but they are basically the same. Unless one really catches your eye, buy one of the brands that your favorite shop sells, because the differences in dealing with them over the life of the bike will outweigh the differences between the bikes.

Don't settle on something too quick... sometimes the search is half the fun

EDIT: Disk brakes are nice if you get good ones... but most disk brakes on sub $1000 bikes suck. A nice set of V's with good pads is better than cheap disk brakes by a good margin, and is easier to deal with as well. Look for a mechanical brake by Avid, and don't bother with the cheap stuff. In a pinch I'd try the Shimano Mechs (M515 I think?) or a Hayes model (HFX-1?), but I'd try for Avid.