I signed up and like the ease of signup and the simplicity of the interface. I was a bit annoyed that I couldn't find a page of features/benefits and that I had to signup to see how it works, but your signup was painless enough that I got over it.

I'm currently using manymoon. They have a similar feed style setup, but the killer features for me are Google Apps/Google Docs integration. I don't know if that's something you'd consider or how difficult it is to do, but I personally wouldn't switch over without those features.

They also do a posterous-style email response to assigned tasks, which means you can comment on a task without logging in. That's pretty cool.

If I were to build an app like this, I would expand on posterous-style email task creation/control (I live out of a BB).