Have a look at https://trello.com/b/hjBDflxp/meteor-roadmap , but I can make a quick resume for you:
* There is no easy/official way for doing joins in subscriptions (you can't join "Posts" and "Comments" in a typical blog example). I'm aware of several plugins that try to implement that, but they all lack official support and quite of them just fail at doing it properly.
* No server-side rendering. Say goodbye to SEO, unless you're willing to follow the prerender.io way.
* No i18n. Should I say anything at all about this one?
* Not even basic forms support. This is the abc of any framework, and yet Meteor doesn't have it.
* Bad routing support
* Not-that-good documentation and examples
So, no, MeteorJS is just not there yet. But the idea is cool and I'm sure if those things get fixed/implemented, it will get quite a big user-base.