Opera is an alright browser. If I had to choose between opera and IE, well, opera all the way. But as long as Firefox remains as extensible and widely supported as it is, I use it. And I close it when I am not using it because d11 is right, the memory usage will literally kill your computer. I have experienced it, researched and will 100% back up what d11 already stated.
PS This part of the thread was horribly

but I can say that folks using IE are

to not at least give Firefox a try.
PPS The smilies window does not render properly on Firefox 2 with the new smilies added.