I recently started a moderately large project in Meteor and I must say, although I was a little apprehensive at the start, I am truly amazed at how far Meteor has come.

Built-in reactivity, latency-compensation and the lot makes development really fun. It feels like a mature platform, the community is growing and is extremely helpful. I would recommend anyone who is still wondering, to just try to build an app or two with it and you will know what I am talking about.

PS. If you are in the Bay Area, they have Dev Shops at their HQ in SF every 4th Thursday: http://www.meetup.com/Meteor-SFBay/events/221409952/