In my experience, the most consistent way to get useful feedback on side projects or prototypes is to engage with people where they already are (Show HN posts for instance, or certain subreddits). My intuition is it would be hard for this kind of site to maintain enough traffic over the long-term for the average submission to actually get feedback. For OP's sake, I hope I'm wrong though!
If this were to take off, I could totally see myself use it to discover new shiny things. It's pretty difficult to discover novel gems among the vast amount of Github repos.
My issue with following a site like this would be burn out from new products. I followed TechCrunch years ago and ended up signing up for so many start up sites. I'm sure 80% of them don't even exist anymore. When I look at cleaning up my password manager it just seems so daunting. I eventually had to remove it from my RSS reader so I could wait and see what might actually hit crucial mass before jumping on board.
