I think even Cro gets crappy FPS on his system running his own maps.
Reminds me of Counter-Strike maps. I used to play around with map making. You could tell the folks that didn't care about any system at all, they just built details into the map. Often it killed the gameplay, because even the high-end systems crapped out or lagged horribly.
Cro definitely makes nice looking maps, but personally I don't want to see 'em outside a screenshot, as far as gameplay's concerned! Not until/unless they've been seriously optimized for performance (best blend of performance/looks)