One issue not addressed yet is compatability -- do you need JavaScript 1.0 compatability or is 1.2 acceptible?

This is an important issue because it significantly affects what you're able to do on the client side -- 1.2 added primitive regexp support (O'Reilly JavaScript guide, starting page 165) as well as more sophisticated array handling (O'Reilly JavaScript guid page 153) which would make your life much, much easier.

Generally speaking, JavaScript 1.0 support corresponds to 3.x browsers (Netscape, IE) and 1.2 was available in the 4.x browsers. Things get trickier when you look at other browsers -- AOL is running IE's engine, but the versions are off so AOL 3 had something like IE 2-level support. Similar issues arise for Opera, iCab, and so on. The key point is, you need to know your audience in order to know what you have to play with.

If you need 1.0 compatability you're going to have to do much more work on the server side unless you want to get into some pretty heavy JavaScript coding (which can bring you to new levels of frustration).

Hope this helps.