We use Meteor at https://pintask.me/ — it's a great fit for application like ours.
We did run into some roadblocks, but there were resolved rather easily. I guess the reason people don't use Meteor much is because of "bad first impression". It launched on Hacker News without having security, authentication, and many other crucial things. So people looked at it, tried it, and then ditched because it didn't do this or that.
Right now, Meteor has really matured. All issues are solved — and solved better than in other frameworks. Yet people still remember that "Meteor is insecure", which has been true in the past, but already isn't.
So, if you're willing to build a large application in Meteor, go for it. I have done it, and I have no regrets.