Gearbox announced at their panel that Borderlands 2 will be featuring skins, unique heads, and a decal/color editor for players to customize each of the classes with. These will be earned by defeating bosses and enemies as well as completing challenges. In addition, anyone that played the first Borderlands will receive a special skin and head. I'm not sure if it was specifically mentioned, but it is possible that this is what badass points are for since those are gained by defeating tougher enemies and bosses.
Along with this news they also announced a dlc character, the Mechromancer, who will be available somewhere around 60-90 days post release. Anyone who pre-orders the game will get this character for free when she becomes available. If you don't pre-order you'll have to pay for the dlc when it makes it's appearance. Not much was said about the class as she is still mostly conceptual, but her concept art is a female who has a robotic arm, and apparently she can control a big robot named D374-TP (Deathtrap). Gametrailers compared Deathtrap to a mix of claptrap and a T-800 Terminator.
Now for the collectors edition news. It will be priced at $149.99 and will include a fairly sizeable red loot chest and a markus bobble head in addition to the game. The entire thing comes packaged within the loot chest.
Honestly I'm most excited for the character class because the Mechromancer idea has been tossed around on their forums ever since it was brought up in a gearbox survey awhile ago. It also means that they have the capability to add more classes in the future in addition to the usual dlc that they put out post-borderlands 1, which could end up being fairly interesting.