I like Derby over Meteor, without question. But Derby is still sorely lacking in server-side logic, particularly auth, which is what drove my Derby project to a halt. What non-trivial apps can one build without any private or authenticated data whatsoever?
Supposedly these features are coming, and I sincerely hope that derby matures into a real-world tool. The RacerJS tech is amazing, and the library is fun to work with.