When I first heard and saw that IE7 was hiding its menu by default and moving main tool buttons beside the tabs, I thought they had the best design to accomplish the "minimum header disturbance" in the industry. Browsing the web should be an HTML thing, where the hosting browser should not get in our legs.
That was before I actually tried customizing IE7's toolbars. I'm a del.icio.us user, and I need my tag and browse buttons, no matter the browser. With FireFox, those buttons can be moved within the main toolbar:
If I hide the excellent "Web Developer Toolbar", I get 119 pixels lost in height, not counting the status bar at the bottom. If FireFox was to allow hiding its menu bar, it would get down to 94 pixels. Not bad.
With IE7, adding the del.icio.us buttons jumps the header height to 130 pixels. See how much empty space we loose:
That's because one cannot move toolbar buttons around so easily. For example, I can't move the del.icio.us buttons within the main toolbar beside the tabs. It forces me to use a full toolbar banner. If I had more toolbars, I could stack them horizontally, thus use the available space more wisely, but in the current state it's pure lost space. It's because of little annoyances like this one that I'm still a FireFox user, even thought IE7 is a damn good browser.