I've recently been using Meteor on a couple small projects and so far like it quite a bit. My main frustration though is unit testing. While there's the official Velocity test runner, documentation and code examples for integrating and effectively using the frameworks is very confusing (I personally use Mocha). I know there's some books and blogs to help alleviate this, but there doesn't seem to be one (or even just a few) de-facto framework/setups to illustrate how to properly unit test Meteor apps.