Borderlands Developers Speak on Improving Gameplay Experience for Second Game
Borderlands 2 will naturally have more guns than the first game, but that’s not the only thing the developers plan to do for us. There seem to be a few major areas in which the developers are focusing on improvement.
They plan to streamline the inventory system, allowing players to mark items as trash and as favorites, to speed up trips to vendors and prevent the sale of alternate equipment. It will also be possible to trade items to specific players instead of just dropping them on the ground. Some modifications, such as vehicles which can seat four players, are designed to keep everyone together. Changes at area borders will help the different maps feel more connected to each other.
Personally, I’m most excited about the proposed inventory improvements. Allowing everyone to hop into one vehicle is nice, but in some cases it may be an explosive equivalent of putting all your eggs in one basket.
Source: VentureBeat

Sounds like they’re doing some good fine tuning here. Little things like tweaking the inventory system can make a massive impact on gameplay.