You know, one of the best measurements of success for an online community is the level of complaints coming in.
No seriously, if you have people complaining that something is not working of that they want to see something different or that you just have it wrong, then you know you have a good audience for what ever your market is. This means these people have passion for your niche. They care about the topic and care enough about the community to want to see it improve. If no one is complaining, then no one cares. Don't take these complaints as a negative in any way. It's free market research and it will also tell you what’s working and what it not. Embrace the level of response and even more importantly embrace the people who are complaining. They will be your champions and thought leaders.
Having run online communities for over 10 years, I've experienced a LOT of complaints, comments, suggestions and yes surprisingly enough, kudos along the way to know what indicates that you have arrived at that critical mass. A good rule of thumb is for every one person who takes the time to complain about something, there are probably 50 more who experienced the same issue but either don't care enough or are not vocal enough to let you, and the rest of the community, know about it. I've taken my most vocal participants and knighted them, so to speak. You make them your group moderators, writers, bloggers or advocates and give them a title within the community. One of them will eventually rise to the level of Tribe Leader and take over running the community for you.