Okay, to start off I'll admit that I am one of the few people that I've heard of going through a period of DPH abuse. This period lasted maybe 4 months or so, and then I completely lost interest in it (strange huh?). For that period I would use DPH at doses from 100mg - 900mg in a night. I wont start talking shit about it, I completely understand the interest in it.
You will NEVER reach a state similar to Alcohol or Benzos with DPH, as the others are saying. However, at low doses it can cause extreme sedation and stupor. I have also found some mild euphoria (usually music based), and orgasms are extremely enhanced (Seriously, you wouldn't expect it. Some of the best orgasm enhancement that I've felt from a drug. If you're going to be abusing DPH anyways, I'd recommend rubbing one out).
ANYWAYS, at doses of 100-150mg you can get that sedation and stupor. At doses around 200mg, you'll be extremely sedated, but you could possibly be entering the tripping realm. 200mg has always been the border between sedation/stupor and delirium for me. If you don't get the effects you desire from 200 or maybe 250mg, then just set the DPH down. You wont get anymore of the positive effects, just a lot more delirium.