First of all,
You don't really need to make the switch
. You can run both IE and Firefox (seeing as how you can't uninstall IE you have to!) at the same time. So, if you download firefox you can test it out to see if it works with that login page. If it does, great!, if not, then just continue to use IE.
I've found that almost everything that works for IE also works for Firefox. In fact, i've yet to find something that doesnt! heh, even microsoft's website works ;)
Hope that answers your question! You'll love Firefox.