Does this game have the kind of loot variety to keep you coming back to the same character, or do you finish it and restart with someone new?
 
Trying to decide between this and Borderlands, and I know I'll play the hell out of either one, just curious about the replay differences.

Well, the loots not too different, it's more about customization through upgrading. Though once you find that weapon you like using, you'll end up upgrading it a ton, and just using it. Occasionally trying other weapons, and finding that you like them, or hate them. And if you like them, you'll start upgrading and using it. 
 
Variety not so much, but it does have replayability with it's New Game Plus that allows you to keep your items and levels, and increase the amount of souls you get from enemies, and the enemies levels. 
 
If you're going for loot, might be better off with Borderlands. It really depends on what you're looking for. Borderlands is a more social experience if you have can have an internet connection.

as much as everybody loves demon souls, no game is going to beat 17+ mil anytime soon.

Loot in Demon's Souls isn't random like Diablo, enemies always drop the same item(s).  Some of their drops are more rare and require high luck/black world tendency (enemies get tougher, rare loot is dropped more often).  You're better off with Borderlands if you're more interested in loot variety.

Thanks for the replies, all.  It looks like time constraints may be the deciding factor.  I need a game I can jump into for thirty minutes at a time and get something done.  Unless I'm mistaken, Demon's Souls ain't that game.

Actually, Demon's Souls can be played in short sessions. You can always continue from where you left off as long as you don't die. Death reset you back to the beginning of a level.