I am having a love affair with Firefox (it’s different to mozilla) and the plugins for it are becoming more widely available and a super new one that uses anonymous proxies within the browser as well as a handy view link in IE option…I have been suprised how similar it is to IE and wonder how narrow the compatability issues are….of say the approximate 8-10k of pages i have looked at I think one was a bit screwy in the graphics dept.
I have to disagree with Spear here as many are turning to it and it is being openly praised left right and centre as a superior alternative to IE. I am glad I did not ignore the hype in this case….even roboform works in it now and that was the only reason I was ever opening IE. 
When I first started web design all pages had to be for 640×480 and in 256 colours max and IT WAS IMPOSSIBLE to get a page to work in IE AND Netscape…these days it is a comparative piece of cake.