I use fire fox for all my on line use. But I have a few applications that won't recognize fire fox as my default browser.
I never had any issues with applications using FireFox nor do I have anything against it, however I find IE to be more catering to me personally in allowing more time doing business and less time figuring.
FireFox IMO is a good browser, I just prefer IE and don't have the adverse issues using it that have been discussed.