The onchange-property works quite nicely, only it will fire a lot when you are typing.
There are use-cases when you have a sort of grid to be entered and you actually only want to save the input when the user hits enter (and loses focus to the next input-widget)
There can be a workaround by making an hidden-button etc. etc.
but what I really would like to see that the OnBlur will be made standard (alongside the Onchange) so we will have less ajax-calls.