Do those myths matter at all? Most of the "myths" stated probably occur in a lot of browsers, not a single one of them is perfect. I use firefox because of the web design features you can implement, IE has tabs too now but yeah as a web designer the choice is easy for me.

Firefox is far from perfect, sometimes it's quite unstable but maybe that's because of all the extra features I installed or just my pc which isn't great either.

I don't know if there are any noticable speed differences between browsers, I think it depends mainly on the websites server you're viewing, not the browser itself.

Maybe it's obvious from this that I don't like IE, but still I think we should try to approach this in a professional way and make our applications work in every browser with a significant amount of users...

Let's just hope that people stop using IE6 soon and IE8 expectations turn into reality so css and other cross browser compatibility issues decrease a bit.