Re: Sluggish movement
Just from personal experience so far, the character does not move like that (though you will get the "rollerskate" effect when doing things like pinpoint jumping, like from one pipe to another).
Probably, eiither your video settings are too high for your hardware, or you may have some corrupt files messing with the rendering. Do you lag all the time, or only in certain spots? Is there a lot of action on the screen when it happens, or not? Also make sure you don't have any background programs running siphoning off processor cycles.