DXM seems to put you into a state a lot like Alcohol, with disinhibition and all that. But alcohol messes up your motor skills completely. I've noticed that DXM kind of changes them in a certain way. It's still possible to play beer pong well (don't combine DXM with alcohol though!) if you focus enough. Same with pool. If you concentrate, you can make a powerful, accurate shot. But if you get lazy, the ball flies off the table or the pool stick doesn't even hit the cue ball.
When I'm getting drunk, I gradually stop caring. But with DXM, I can shake the feeling and concentrate hard for a moment.

My theory is that while alcohol just gives you a general clumsiness, you get a sort of tunnel vision of concentration from DXM. You can focus on one thing and do it very well, but everything else leaves the picture. So when you're talking to the person you're playing while making a shot, that's when your pool stick is going to rip the billiard fabric.

This may be where the "robo-walk" phenomenon comes from (a weird gait many people say they have when they're on DXM). You let your legs just do their thing while you're concentrating on thinking / looking around / talking, and they eventually get lazy and you start walking funny.

I remember writing in one of my journals that we should replace all cigarettes with joints and all alcohol with cough syrup. The former would definitely be great, but I think the latter would cause more violence, as DXM has a stimulant/analgesic sort of effect that could be dangerous.
I think I wrote that with just the health problems of those drugs in mind though. Like I've said before, a lot still isn't known about DXM, but so far for me, it seems like it has less health problems than alcohol. Don't take my word for it though.