Just to mix it up a little bit, i will say my dad is very functioning.
He has cut back since his A wife died last year, but he was drinking bottles of wine a night and has drank every night for as long as I can remember.
He never missed a day of work (that I know of)
He never got in a car accident (that I know of)
He has never had any medical issues related to it (that I know of)
He never had a problem with his partners (that I know of, my mom excluded...not that it was the reason they split).
My sis and I avoid calling him in the evening cuz he'll be drunk-sappy and it is annoying. But other than that, it has never slowed him down!
Either I am missing things or he is the rare 1 in a million that has weathered alcoholism without falling apart!