It is a console to PC port and they didn't update the controls on the PC at all.
They are actually quite playable, although the camera does present some problems here and there; Since looking around was originally planned for analog controllers, when you look up or down with a mouse, the screen automatically slowly resets to center of the screen, so you have to keep moving the mouse up or down. This is because of the analog controller sends output constantly, while the mouse sends it only when moved.
Aside from the control/camera problems, the game features a nice storyline and a good pacing between stealth and action missions. The half-electronic, half-orchestral soundtrack is pretty amazing as well.
If you don't easily get frustrated with some minor control problems (read: have enjoyed other console ports on the PC before), it's a fine shooter, well worth the purchase imo.