It's a set of mods, it just increases the game speed :P They originally took the PC speed, and docked it 20% to make it more playable with a controller, I have 2 mods right now, one of them puts it at the same speed, and the other puts it 20% FASTER than the PC version xD It's pretty hectic :)
Mods make Unreal what it's god given name was set out to be, unreal! :) I've downloaded at least 100 mods ranging from new stages, different character models, different weapons, enhanced vehicles, jetpacks! Predator armor (your invisible unless you get hit or shoot :P ), etc etc... it almost seems limitless sometimes XD. And I can now download them from the PS3 browser :) Which is just awesome!
I am DEFINITELY jealous of the split screen ^^ but that could totally be added in a patch :) Unless that of course remains exclusive, which it honestly might :D. But split screen doesn't equal anywhere near as much value as the self customization you can give the unreal franchise. I'll dump hours into the game just to test out some new mods or stages :P