I was using Mozilla since Version 0.9 (if memory serves), so I switched to Firebird/Firebox and Thunderbird almost as soon as they were available.
And no, Fyron isn't involved in neither, but merely the amount of viruses I received through Outlook
(formatting is fun and all, but...)
IE serves one single purpose: to take care of some sites which will not run for no apparent reason (read, because I didn't set up my browser correctly).