It also seems that you can easily have a "testing mode" where you run the preprocessing client side when you are just building the app, and then when you deploy like "for real", run the preprocessing server side to keep things fast(er).
If the site gets too hammered, then you could even have it switch, where an overloaded server tells clients to preprocess for themselves while the server catches up. This would be an interesting way to handle spikes in usage (like now for example)
Presumably the code doesn't change very often, so we actually just preprocess it once per revision and serve up the static files, so there's no extra load on the server or the client.
If the site gets too hammered, then you could even have it switch, where an overloaded server tells clients to preprocess for themselves while the server catches up. This would be an interesting way to handle spikes in usage (like now for example)