Yeah, it's a fair amount, like 600mg HCl / 800mg Nap.
Of course those are aproximate, it depends on the user - body weight, sex, tollerance, general fucked up raver neurochemistry, etc.. basically, once you hit that amount, you can take more and more - you wont get any more euphoria or warmth/bliss/etc.. but rather just an increase in the nasty side effects.. I am sure it's harsh on some organ - liver, kidney, heart, whatever...
For the opiate newbie/virgin, Darvon/Darvocet can be fun to give the general idea of what "warmth" and "bliss" is, but for anyone that has had real drugs I don't recomend you waste yer time with it (unless you get a REALLY good deal or it's given toyou - NEVER turn down free drugs, it's rude)..