Understandable-- but if you are productive on Meteor today, or you and your team have already committed to learning about it, I would suggest that you should see that through. This kind of uncertainty/doubt around open source frameworks is par for the course, unfortunately, and I think it would be a real shame to stop before you've at least built a prototype with the technology you've already invested time with (particularly since so much of a v1 is figuring out the interface/interaction design anyways, y'know?) Just my 2¢.