it can be quite nice to get the client to run the display cruft while the server gets on with someone else.

Is it a closed environment where you have control over the clients? If not, I won't be able to view your site and a lot of other people won't either. Cause I don't usually enable JS - or am sometimes powered by lynx/links.

JS can also alow you to do much of the input validation on the client thus saving considerable effort in making the server reject malformed queries politely.

Yikes! What stops anyone from using a saved and edited HTML page or LWP or one of the million other possibilities to maliciously send you malformed input?

Don't Trust The Client.

Whatever you do, Don't Trust The Client.

Makeshifts last the longest.