My humble view - Sadly, I see it as another opportunity for eruptions of discontent and argument - which would then have to be removed or refereed by the mods. There is always the risk that someone with malicious intent or what they perceive to be an unresolved grievance might log poor feedback, sadly even untruthful feedback?
I've had many transactions now on the site, buying and selling. Maybe I've been lucky, but I'd rate all my experiences as 4-5 stars and I hope the people I have done business with have felt the same - but I cannot be sure of other's feelings. But I've been cautious when it particularly mattered (higher $s usually) - it was my job to protect my interests, not someone else's.
I've had people PM me re issues, sellers and with their thoughts on goods in which I expressed an interest in the thread - PMs whose advice I have accepted or not, but all of which I have appreciated - I suggest that we leave it that way - informal private advice being shared around.
Sorry for being the wet blanket. Perhaps I'm too pessimistic and we need to give it a go at least?