I track my stats for when I play without drinking and when I play with drinking and I have 100's of live sessions with drinking and the average is shockingly in favor of me playing while drinking (albeit by an almost meaningless amount) - I do not think it makes you play better, but I do think that people if they sit down and see you with a drink will throw you that extra bet or two here and there as they think you're drunk.
So.... playing while drunk is horrible, but I do think some people can play effectively having a cocktail every X amount of time, where X is the amount of time you require between drinks to not affect your mental faculties.
Barron Vangor Toth
www.BarronVangorToth.com