When completely sober, i think to much and i overengineer (overthink) stuff... Programming is just slower...
(Think DDD-like programming)
1 beer is enough to get very concentrated... Just don't overdue it (and don't make a habbit of it).
I only do it when i need to get things done, when time is limited... Never had serious bugs (Windows ME like) though :-P
It happens once in the 2 months and mostly it's for 2-3 days in the weekend (non-stop), with some light kind of music (Enya or concentration like mp3's) and headphones.
Yeah, i'm a nerd then :P