The plot could be better, but the gameplay is really cool, although the difficulty curve is kinda messed up. You start operating people from tumors and end up with inmortal supersonic parasites. I had to check a guide for most of the second half of the levels, but there wasn't a level I had to restart more than 10 times.
Also, the boss rush was anticlimatic as hell, the game should have used Savato (the first encounter) as the final boss. It just felt as filler while the story finished developing.