I played almost the whole thing using a USB game controller (a Saitek P2500, for the inquisitive). I just left auto-targeting on, and swimming/aiming etc was no problem. Being able to use an analog stick for moving about seemed infinitely easier than using the mouse or keyboard, evevn if I did have a bit of a time with button-function overlap. Also, since you're using your thumbs instead of clicking, you can pretty much kick the crap out of anything and everything with energy form shots, even unenhanced. The whole game seemed quite easy, although still immensely enjoyable.