aside of IE6, what I don't get is this: in IE8 you have the option to render as IE7, IE8, or IE8 in compatibility view (for older browsers, like, say, Firefox, Safari or Chrome

). Wouldn't it be way easier, logical, and way less stupid to render everything in "compatibility view for older browsers like FF, Safari, Chrome, yadda yadda yadda" and problem solved? Not like you need a rocket engineer to figure that out (or code the rendering modes, as we're at it)
Or, just for the sake of it, one rendering engine for all of IE versions so we don't need to code different versions for IE6, IE7 and IE8? Yeah, I'm that naive....