tested on ff/tb 1.5-3
i use this with the default theme + CuteMenus - Crystal SVG (not sure how it looks on other themes)
http://img490.imageshack.us/my.php?image=screenshot2fb9.png (older screenshot)
i didnt write all of this some of it was borrowed from other places
Update: fixed tooltips disappearing
Update2: changed menu/mouseover/tree row(dropdown autocomplete) borders
Update3: changed the tabs and other stuff i've forgotten
Update4:changed hover for menuitems from border to a lightgrey background
Update5:changed some more stuff
removed main menu height, it was hiding the menus on ff2
Update6: small touchups
removed tab styles see Firefox/ThunderBird - Tab Colours/Settings
Update7:slimmed the addons items ff2/3
removed button/checkbox mouseover
removed mouseover borders/left old borders
changed menu/menuitem highlight colour
removed console2 styles
urlbar/searchbox rounded borders
increased livemark menupopup max-height
reduced width of search box when customize toolbar is open
removed statusbar padding
a few changes
removed bold mouseover from buttons/checkboxes
added max height 16px for main toolbar
removed slim extension list ff2 use this instead Firefox - Add-ons - reduce size
changed width of toolbar spaces
added border to the top of the find bar
removed button focus