We moved the button and a number of the tabs in Firefox devtools to be more like the order in Firebug and Chrome devtools. Here's a screenshot from current Nightly: https://i.imgur.com/EmVIZYO.png
New devtools are much improved however would it be possible to remove the dotted lines whilst inspecting an element (toggled option would be fine), just seems to get in the way of things.
http://i.imgur.com/W9Z5jBJ.png