i've seen it on my computer in both setting and to be completely honest.... i dont see that big of a difference...
medium settings still has all the real time lighting, body physics and all...
i know that ultra high does have some things that are better but i just cant notice it... therefore i could hardly care less...
and Mackey if you want a game where u just go around and kick ass...
Painkiller is definatly for you...
check that game out... its by far on of the most underappreciated games out there...