Same here, I feel like there's to much magic to Meteor. Like how does it know something has changed in the database? It must be querying the same queries over and over again. And that's just one of many things.
Meteor seems to me like a tool for people who are not able (or have no capacity) to learn javascript or the technologies which they need to work with to achieve their implementation, so they jump into Meteor because it promises a lot. But they lack optimisation and for me even micro-optimisation is important.