It's strange to bring up the point of loading session info from a template because "In scenarios where the latency is too high, the experience is simply horrend

It's strange to bring up the point of loading session info from a template because "In scenarios where the latency is too high, the experience is simply horrendous. Remember, fast is good. Users want fast.", but then say "On a related note, I never find myself doing validations and that sort of thing on the client, as I find it a pain in the ass to do the double work of checking on both the server and the client. You should though handle errors coming from the server (API) and be informative enough through error messages." Either you're not checking anything until everything is posted back to the server, or roundtripping to the server for every field. Either way, not doing any client side validation is going to have a lot more noticable effect on UX than grabbing session info directly.