Large open spaces with a superabundance of items which could have been more stragetically positioned. With this many items its going to hit your frame rate if your not displaying simple items. There is a pretty chunky feel to the architecture, and with bits of tech, gothic detailing and ochre walls the elements just don't pull together into a cohesive theme. For all that its a fun game with all the weapons you are never short of fire power and the open layout leads to some fun shoot outs. Bots play pretty well, but don't go for the BFG.
Play for fun on a high spec system.