I think the ones that drop on the 15th day are those from the Chinese mainland registries. Those outside registries seem to drop earlier as dvdrip as said.
I can say that the interest in the resellers are growing this time. Due to the limitation of broadbrand and internet acessess, some keen resellers book the whole internet bar and invite friends to help to reg manually.
It seem the the winners are those who use domain dropping software and those who work in telecom companies (maybe better infrastructure)
The keenest competition was on 2 digit alphabets and numbers, example :
aa.cn
pp.cn
11.cn
33.cn
For me, I was dozing off when it dropped around late 3 am morning on Apr 2
%+| , better luck next year