I like to use the WIP board from time to time when I'm working on something, although I haven't made as much use of it as I would like. When I'm trying to decide, say, between a couple different ways of presenting a lyric, or a couple different possible wordings of a line or two--I'll post the choices to the WIP board and ask for input.
I've posted two kinds of songs to the "Finished" board: 1. those I don't expect to be able to have produced anytime soon, but I consider them finished and 2. those I've had professionally produced (the kind that costs money). Ian mentioned being hesitant to offer too much criticism in the second case, and I can understand that. Some people may have their song "in stone" by that time. But I haven't. The "Finished" board is the last step. My producer will make tweaks for me, if I want them, based on feedback I get on the "Finished" board. My purpose in posting to the "Finished" board is to present a song I think of as finished BUT I want to find out if there are still improvements I could make.
In my opinion, that's how it should be. If the song can no longer be tweaked, why post it for feedback? In fact, it seems a little surprising to me that the "Finished" board gets more action than "WIP" for just that reason. And what happens is people post stuff they don't really consider finished in the more active board because it is more active and they're more likely to get feedback.
In spite of all that, I have had very good results when I post to WIP.
Vicki