The boss fight at the end, though fun, was almost complete identical to the original game. And how you finally defeat the boss is a bit illogical, though I suppose when it's placed in a game based on destroying the laws of physics, that can be justifiable. Nevertheless, it's a spectacular ending, and what comes after it neatly wraps up the game. Unfortunately, there isn't a sequel hook (at least not an obvious one), so it may end up that this is the last that we will ever see of Chell and GLaDOS. If this is the case, then that would be fine by me. The game ending is fulfilling, and pleasantly wraps up everything. The ending song is catchy as hell also; dare I say, better than Still Alive?