So... today I put in effort into expanding the now committed AHAH Forms API to extend to all form elements. This means all kinds of effortless page updating on text area changes, radio buttons... you name it. The first target: the blocks page! Does this seem useful or annoying to you guys? Admittedly, the weight problem needs to be solved in general, but I'm not sure if this is the solution. Notice that different regions disappear and appear as needed, no javascript in the block module involved at all. In any case, it made a great test-case scenario!

See the patch for Drupal 6: http://drupal.org/node/157752