The only drugs I ever have any significant problems driving on are alcohol, marijuana and really high doses of heroin that cause me to go cross-eyed.
I have driven on every single type of drug I have ever used. This basically covers every drug you could ever abuse. Downers, uppers, psychedelics, depressants, stimulants, dissociatives, entheogens.. you name it, I've done. Low doses to ridiculously high doses.
And I disagree with statments about not driving on dissociatives or downers or ridiculously high doses of psychedelics. Sure, it's a better idea NOT to, but it's not neccessarily going to negatively effect everyone's driving. It's a matter of being very conscious of how the drugs are effecting you.
I can't drive for shit even if I only smoke half a joint. But I learned how to parallel park on 6 hits of better than average LSD. Most psychedelics and ecstasy actually improve my coordination for some reason. There have been times I was hallucinating so hard I could hardly tell what I was looking at, but man, I could keep the wheel as straight as a razor and stop dead on a dime.