Firefox is great, although it doesn't work with everything out there, it is 98% friendly...
the other 2% I'd go with IE.
I have to be honest...if one can upgrade to IE 7, it's better that they do that than staying with IE6
reason is that IE 6 has MORE vulnerabilities than IE 7
usually, when the patches are corrected, they'll be OK...
IE 7 has taken it's lessons from Firefox so it is actually emulating the firefox browser...meaning it is following the leader...
you know, monkey see, monkey do? (Every pun intended...)
anyways, I am sure more experts will chime in and agree/disagree....LOL