Currently the radio tag only has an onchange attribute, this is pretty much useless for many purposes

Quoting from

http://msdn.microsoft.com/library/default.asp?url=/workshop/author/dhtml/reference/events/onchange.asp

""This event is fired when the contents are committed and not while the value is changing. For example, on a text box, this event is not fired while the user is typing, but rather when the user commits the change by leaving the text box that has focus""

This means if you for instance want to do a roundtrip when a user changes an option you can't use onchange for that consistently across browsers

A crude workaround would be to use javascript like this

function shippingMethodChanged() {

}

window.onload = function() {
  with(document.forms[0]) {
    for (i=0;i<shippingMethod.length;i++) {
      shippingMethod[i].onclick = shippingMethodChanged;
    }
  }
}

But i'd be nicer to have a onclick param added