Runic Games have released the first trailer showing off gameplay footage of Torchlight 2. Not only do we get a glimpse of the new weather system and several new locations, we get our first peak at the co-op action. In fact, the entire trailer is focused on co-op play and how it was the number one asked for feature of the original. You see that - developers do listen to our feedback.
From the trailer it appears that co-op consists of at least 4 players, though from what I've heard, they don't have a set number of players yet. It's also hard to discern what the classes are that are being played, but the trailer surely whets our appetite for more! Right now Torchlight 2 is set for a Spring 2011 release on the PC and Mac.