Up until 1.0 I'm mostly measuring success by contributors/community enthusiasm. After 1.0 (which should be out this year I think) the focus is going to shift from adding all the main features to getting people using it and continued polish on the core. The summer projects we have going are pretty much the major pieces needed to get us to that point. Until 1.0 it's hard for me to feel that it's realistic to assess success based on usage; free software people tend to be more forgiving about major pieces not being totally there, other people, not so much. And community-wise we're doing good: we've got somewhere around 75 contributors and many, many active people currently. Overall I'm feeling good about the state of things. I'm not totally sure that's the right way to go, but it's also pretty much the way to go as constrained by the momentum of community and what's happening successfully where for now. :)