It's possible that I just missed what was so useful about the site in question... but it's also possible that those who didn't like the site didn't comment. I didn't like the site, or indeed care about it at all, and I'm not the type to want to hurt someone's feelings, so I didn't comment on it.

Friends or not, I think the best feedback is likely from users who have the problem you're trying to solve. The best question is probably "why wouldn't you use this thing?"