The interesting bit of isomorphic applications isn't the fact that you can use JS on the server. For me, it's that you can keep all your UI and UI-related logic written in one language, and have your business logic, data fetching, and everything else in whatever language you prefer.

This has many benefits like code reusability and not having to write placeholders/render code twice -- in two different languages.

Thank you! I will never understand this push towards "isomorphism". Why do you want to use more javascript? I use javascript because I have to, not because I want to. I love being able to work in the language of my choice on the server.

Furthermore, I'm not convinced it's a good thing to blur the lines between client and server. Or in other words, I think it's a good thing for the developer to be thinking about the differences and the ramifications of code on the client vs. code on the server. The whole thing reminds me of the EJB days, where we were sold on the idea of not having to think about the implications of local vs. remote objects. In reality, no matter how you hide it in the syntax, those kinds of distinctions have consequences, and treating client code like it's server code or vice versa just seems like a bad idea to me.