i experienced no slowdowns, if you are experiencing some then try to set the process to high and tweak your windows as suggested in some of the threads... it solved the prob for me..
I get normal speeds on my P4 2.6 ghz, Ati 9700 pro. There is a bit of slowdown depending on what's going on onscreen though... and certain characters seem to slow it down as well. Particularly Blackheart. Too bad--he's one of my favorites...