hmm,
As I’m finishing one new form, I felt on your post.
Afaik, the eform validation process take place after the user has clicked the submit button.
So I guess the actions won’t take place in some "ajaxsified" manner.
The php rebuilds the page with some element that would differs from the original state
(new class added for required field or invalid data regarding eform validation rules)
see doc: &invalidClass=`not-valid` and &requiredClass (have a look here :
http://spreadsheets.google.com/pub?key=pHJSI5ye5FxqRfh1nEPCnJA&gid=10)
If we want to animate somehow the DOM for item that displays some error, I can see one easy way (but I m not a php guru):
on the returned page, you hide(fast) all item targeted by the errors classes eform put, and callback some animate() for those, in order to make them reappear in a funny way.
Another way could be to use one of the numerous jQuery scripts you could find to handle "on the fly" the filling of the form.