1. It is EASY. Like, really, really easy. I went through Discover Meteor in less than two days, and was easily imagining how to implement other applications after one run through.
2. It is accessible. The free deployment on the .meteor domain, the open source sensibilities, the constant growth. It's got a good snowballs path going on growth.
3. The developers really believe in this product. Everyone on HN has an opinion of the best way to develop software. That said, I feel there is a certain intrinsic respect we share for one another here(MOST of the time ;]) and to ignore developers who are as passionate as these guys building a functional product that clearly has room to grow, we'd be fools to ignore them if we didn't have the time and/or interest (and the interest is hard to not have with what it offers so easily).
This article seems to really further my faith in Meteor. Stopping the "pull and diff" method is a great first step towards making it truly scalable in the sense other frameworks have developed the capability.