i think forums are much less open than this thread seems to be.  i've got several people favorited i've never once seen post outside of this thread.  
i think w.i.p. is completely different than a review of a finished product.  i also think that this effort will become exactly what people feared as a forum: a clique with popular favorites.   and while i'll go with an open effort, once this becomes more about personality, i'm not very interested. 

i already count 60+ forums.  i don't see how a new w.i.p./critique forum will beat the odds and be any more popular than the developer's forum or the art theory one.  but i don't think that anyone will favorite people after there's a forum, and many will drop favorites. it's really easy to click on a forum and not so easy to add everyone and then try to keep up with the postings. contributing is a large part of all this, and forums are very, very passive.  the only time you'd get notification is after you post, not when someone posted an image.  i would lay money on this petering out in a month or so if there's a forum, but that's just my money  ;D. 

while someone can really contribute a lot personally by commenting in the galleries where it's visible, in a forum it only makes a difference if people go there in the first place.

personally, if i wanted help with a w.i.p., i'd post here.  i've seen tons of people do that already.  why would there need to be another forum where very few people go?

edited to add:
there is a better way.  it's called social software.  if this site supported groups, with an automatic notification of a group member's gallery posting, it would be great.   your reached a limit?  that's amazing, if so.  i've been to people's home pages where they had more than 7 or 8 pages of favorites.