Just how powerful are Susan Storms Force fields?

[raven]

I have been thinking for sometime about the question. I would like to know your views on the matter, I personally believe she is seriously under-rated power wise and is down played to other superheroes in games and in comics and movies e.g. F4 first game her force field could contain a supernova blast but not survive a double fisted slam on her force field or a missile attack. I would also like to know what she uses to control them e.g is it dependant on concentration or what. thank you! ^^