I've always been rather fond of Opera Web Browser, but due to being dependent on firefox and firebug I've not been able to make a full switch. Times are changing. With the new Opera 9.5 Developer Tools (Dragonfly are supplied as well, and boy are they nice. With many of the same features I rely on in firebug(like mouse over elements, view CSS and see which styles are overwritten) I may be able to make the switch. I definitely recommend giving it a try!