Just gets better.
File attachment has the same problem as pretty much every other dialog box in a WA extension. Pick or type what you want, then click somewhere else in the dialog box to set the field. Otherwise, your attachment will not be saved when you click OK.
Once you go back to do it AGAIN though you will find that your email will arrive with the attachment and nothing in the body except a 0.
Remove the attachment and the email will arrive with the proper body.
So glad I upgraded. 2.5 hrs invested now in sending 2 emails on submit.