The only downside is no multiplayer
I believe the sequel to Torchlight is supposed to have multiplayer. They're working on it now, but I think they got sidetracked by the XBLA port.
Real fun game, got a bit repetitive later on though. I'm hoping they expand it on the next release. More classes, more abilities, etc... It's a good accessible-Diablo that is less intimidating, I even got the wife to play it for a bit! She wouldn't touch Diablo with a 10-foot-pole...