Jason, your experience with firefox is quite uncommon. Firefox actually has more protection, much more, than Internet Explorer 6 - more than likely, you installed the browser while your virus protectiuon was running thereby causing a bad installation. If you are running Norton or MacAfee antivirus, they are your culprits, not Firefox.
I have IE and Firefox on all my computers and IE7 Beta3 on one of mine. Firefox is basically the old Netscape browser and runs like it. It caches much slower but reads the cache better than IE6. For VMK, I prefer it because of its superior cache reading qualities. I do not use it, however, when I want to stream content from websites. IE handle that best.