Through the 2 that I had, only 1 went above 3.6 without crazy voltage. I had it to 4.0 booting into windows on 1.6, but anything outside of launching CPUz would crash and burn. I ran it at 3.8 ~1.55 for a while before the memory controller started dieing. lol The one AMD sent from RMA would hit 3.7 ~1.55, but not very stable, and I was done killing chips.
When they first released many people thought that the lack of a 4th core would give lower temps and a higher overclock. But it seems there is a "voltage leak" that comes with a dead core (probably just a theory).
3.6 is a nice OC with one of those chips and 3.8 is darn nice. Your next step should be working with the FSB. Sometimes lowering the multi and raising it can get you a few hundred extra Mhz.
I also noticed you have an ASUS motherboard. The 3 M4N72-E's that I went through would hit 2600 HT/2600 NB easy. Good luck!
Oh, and check out Dolk's guide to AM2+ overclocking if you haven't already, there's some good stuff there.