This pattern is very interesting, although I'm finding I develop a quite a bit faster on server side frameworks like Flask/Django... One thing I don't like about the pattern is that you have to send the templates to all the users (static), even users that don't have access to the those pages (for example, an admin page). Have you run into this? Of course you could also send the templates via JSON...
Well in my case I wrote a little packer / minifier for compiled Jade (http://jade-lang.com/) templates and serve them as a single JavaScript file.
When you have different templates based on user rights, you should probably make different packed template files and serve them only to users with the proper cookie / session rights.
I'd serve an admin page / app at a specific URL and then it would reference the proper template JS file (or whatever you're using).
Either way I wouldn't worry about the extra few bytes served for rarely used templates, just make sure the template file is properly cached. Or serve it as a different file and load it asynchronously when needed.
If anyone's interested, I put up the code I wrote for packing Jade templates into a single file and serving them to the client with Express: http://pastebin.com/kRtCJHYH (feel free to do whatever you want with it)
I found there were very few good alternatives for using Jade template client-side. The only one that seems promising is JadeVu (https://github.com/LearnBoost/jadevu/) but the approach is very different.
Oh yes, its not the page size I worry about, but whether the template already has some info that you don't want to share (OK, probably most interesting info is dynamic, but anyway)
