Internet Explorer 7: Microsoft doesn't care about usability
Just a general rant:
The top menu bar of IE 6 is completely configurable. You can add or remove buttons and change the appearance and generally make it just how you'd like.
Good luck trying that with IE 7.
In typical Microsoft form, some idiot decided that you didn't need to be able to reduce the size of the menu bar area.
Here's IE 6 with the top menu customized to be very small,
and here's what you get in IE 7