I went looking for an answer for this awhile back and came up with a few answers from more than one forum.
First I understand that it is a AOSP build, kinda like the nexus, pure google without the sense, touchwiz other stuff on top of it
Next, i think one of the answers that I came across is that it is based solely on "final" releases and not leaks and patchwork stuff.
Other than that, I got nothing. I havent really given it a chance because I really don't want my phone to have glaring issues like the current build (6.2) has (no camcorder, no MMS).
Do not take that remark as me knocking the build, it is just preference. I know he is working hard on it, and with the Froyo source released it should be ready to go full blown sometime in the near future.
Alos, I am sure there are other great things that I don't know anything about and someone will fill in the blanks