One of the advantages of the Mathematica proposal was our ability to regularly communicate within the StackOverflow Mathematica chatroom. This allowed us to build and maintain a core group of users. It is this core group, that I believe helped us quickly pass through to beta after the original proposal was closed. We were able to work out a number of details and coordinate our efforts at rallying the larger Mathematica community behind our proposal. The vast majority of proposals do not have this ability, and I think it hinders their development.
So, why can't each proposal be granted their own chat room?
I think just allowing the top level "questions about this proposal" to be distinct from the discuss.area51... questions would help as well. I didn't even realize they were linked until I started getting hate-notices for the way I was conducting my marketing research..... (helps to know where people are coming from so you can go back to the well.....)