I was forced to fill out an XFA form (that was pretending to be a PDF) from the Canadian government and the experience left me feeling completely subjugated. The lengths that Adobe go to to make sure that you have the most frustrating experience possible is unbelieveable. Searching for alternatives or help leads you to either: be forced to buy their premium software (or a licensed equivalent) or subscribe for Adobe’s online tools. Why is this propriety format allowed in government forms? What is so fantastic/irreplaceable about this format?
Also to your point about not having an issue with Firefox, I read that Firefox recently implemented an XFA reader in their browser but the issue is that most of the javascript is not supported so the functionality of the form is not guaranteed to work.