I dislike protobuf for the reason that the generated code is often quite bad (in terms of the interface in the language you are using) and in external projects it's often a manual step (sometimes with additional headache of protoc2 vs protoc3) to just build the project. In terms of message specification it's quite good though.
This is the reason we opted for building our own code gen system instead of Thrift or Protobuf: they both generate really ugly code in the languages we wanted to use
