Normally, follow up games tend to be boring and more of the same, but mass effect 2 is not one of those, its just great.
The game-play is also great, enemies try to flank you and they will use their powers to try and defeat you, still there are some glitches that you can use to your advantage. What I can say for certain is that you can not just run forward and blast off your first spell, if you try you will die... Use technique to get through the levels. You will also find some time to have fun in battles, by throwing people off cliffs with your biotic or freezing them.
Still at this point there is only one bug that I have found that is frustrating, sometimes when walking into an corner or something you will get pushed off map and you wont be able to get back without loading, do not save the game at that point since you will be stuck there.
To wrap this up: There is hardly anything I can complain about, maybe the mining system, its boring and time consuming and you will mostly end up with not giving a rats ass about it and just continue with the story.