Well I would guess that the Anti-e properties coupled with the androgenic properties are what make it an effective pre-contest compound for myself. I am speaking for myself only, but in my experience at a dose of 4-6 tabs per day I notice a significant difference in hardness. I usually start it around 8 weeks out. I do use Arimidex throughout my cycle and increase dose as I get nearer to show (around 2mg daily last 4 weeks). I also add in Cytadren last 4 weeks which also works very good for me in terms of drying out and preserving muscle in a catabolic state.
I have had pretty good success using this protocol, cant promise it will work the same for everyone.