The newest issue of Game Informer has a big pile of details about Borderlands 2, and while Gearbox isn't reinventing the wheel or anything, they are planning a number of changes that should keep things interesting for players who stretched the first game to its limit. First up, there will be four new playable characters with new abilities, including Salvador, the burly fellow with the Amish beard you see to the right. Salvador is a Gunzerker, which allows him to dual wield any two guns. He is also a big fan of ringer tees and biore pore strips. The previous game's characters will pop up as NPCs, but it's not clear exactly what role they'll play.
Missions will be dynamic, meaning if you fail one, or if something goes wrong, it can shape the storyline for the rest of the game. This might imply an increased focus on story vs. shooting and looting this time around, or it could just be a matter of having certain characters or conversations change a little bit as you play the game. Still, it's a neat idea.
The weapons will be brand new (although they'll still be guns so, they probably won't be that new), there will be more vehicles and enemy types, and they've added an element called Eridium that can improve the stats of items in game, or used as a currency.
More details are said to be forthcoming at Gamescom, so I wouldn't be surprised if trailers or gameplay footage starts popping up around then.
Borderlands 2 detailed in Game Informer [Gematsu]