my rebbe told us a pretty good rule of thumb: it is a mitzvah to get drunk on purim if you know how to get drunk l’sheim shamayim.
if getting drunk will cause one to be oveir on other mitzvos (ie, bentching: chiyuv d’oraysa. kibud horim: chiyuv d’oraysa. ona’a: chiyuv d’oraysa. you get my drift…) then you cannot get drunk. you can still fulfill the mitzvah by sleeping but you won’t be oveir on countless other mitzvos through it.
v’hameivin, yavin