This sequel is an improvement over the original Borderlands. The basic shoot everything and look for loot game-play remains, but the level designs and weapons are far more interesting. There is a much greater emphasis on verticality, cover and movement. The first game seems flat and empty compared to this.
Multiplayer co-op is still the way to go because the story, although a bit more focused, is still a bit of an after thought. At least you are given a villain to pursue even though you really don't care why he is doing what he is doing.