Good to hear. The way I (and most people) decide which frontend libraries to use are by seeing them in action. Then I can decide after evaluating it technically if it's something I want to use or not.
Looking forward to doing that with SproutCore.
This obviously makes it a tougher sell. However, when people actually start building apps, their responses are overwhelmingly positive and they're very happy with their decision. I would much rather this problem than vise versa. We're going to work on the outward facing stuff, I promise.