However, I played using the Restored Content mod - a fan created mod using the original resources, completing the game. Still great, it did mar an otherwise superb game. So why not 100%? Well, to be honest, the game simply wasn't finished, and notoriously is missing a lot of content, including an entire planet, and several sub-plots and quests. The designers acknowledged that the first game was great, beloved even, and chose wisely to not deviate from what made it great in the sequel.
Combat is mostly the same (excellent) combat from the first game, with new powers, feats, weapons, etc, and non-combat interaction and exploration is very similar, almost identical in fact, to the original. The story is, in my opinion, even better than the first game.
What a superb game! It takes everything that made the first game great and adds on several layers of depth.