I'd say the backbone comparison is pretty apt, but I've always felt both strived to be "libraries" of structural building blocks rather than frameworks (for better or worse).

Writing express servers feels a lot like writing a Ruby server at the Rack level. To people that are used to Rails/Django, it feels a lot more manual and painstaking. While I personally like the clarity of request flow and modularity that I get using express, there are definitely some friction points (picking the best model layer, quickly picking up a new codebase, generating admin UI, to name a few).

Yeah, though I still think its a bit thin to act as a good backend. I'm waiting for a better DB/model/controller framework to serve APIs.