"War Stories" (which is an episode later in the series) has some torture in it, but most of the torture is off screen and the emotional trauma to the audience is screaming. We do see a few cuts being made, but nothing too violent.

In all, it's fairly low gore. There are some gun shot wounds (and repairs to those wounds), but not a lot of shots of people bleeding and stuff. A lot of the violence (that's messier than a single gun shot wound or stab) is implied.

None of Whedon's stuff (thus far) has been all that gorey (despite dealing with vampires).

And Firefly is pretty much the best show ever. Every time I watch it, I make it about five minutes in before I announce, "I'd forgotten how good this show is!" ♥