This is for (very) personal use and I have made no attempts to get it working with any other setup (addons, toolbar-layout and such) than my own.
Update: Yup.
@namespace url(http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul); vbox { border: 0 !important; }#main-window { }#sidebar-header { display:none !important; }tree { margin: 0 !important; border: 0 !important; background: none !important; }#tabpanels { padding:0 !important; margin: 0 !important; }#browser { border-bottom: 1px solid rgba(55,55,55,.5) !important; }#navigator-toolbox { background: rgba(5,5,5,.7) !important; border: 1px solid rgba(0,0,0,.6) !important; }#main-window[sizemode=maximized] #navigator-toolbox { border-right:0 !important; border-left:0 !important; }#navigator-toolbox #nav-bar { background: none !important; padding:0 !important; border:0 !important; border-bottom: 1px solid rgba(0,0,0,.8) !important; height:27px !important; margin: 0 !important; }#navigator-toolbox #nav-bar .toolbarbutton-1 { border:0 !important; opacity:0.2 !important; }#navigator-toolbox #nav-bar .toolbarbutton-1:hover { opacity:0.6 !important; -moz-appearance:none !important; }#nav-bar .toolbarbutton-menubutton-button:hover { border:0 !important; }#urlbar { -moz-appearance:none !important; background: rgba(255,255,255,.8) !important; margin:0 0 0 2px !important; border:0 !important; border-radius:0 !important; color: #151515 !important; height:26px !important; }#urlbar .autocomplete-textbox-container { margin-top: 0 !important; margin-left: 0 !important; }#urlbar[level="high"] #identity-box { background-image: -moz-linear-gradient(rgba(115,183,48,0.8), rgba(115,183,48,0.6)) !important; }#urlbar[level="broken"] #identity-box { background-image: -moz-linear-gradient(rgba(253,1,0,0.8), rgba(253,1,0,0.6)) !important; }#urlbar[focused] { background-image: -moz-linear-gradient(rgba(255,255,255,1.0), rgba255,255,255,1.0)) !important; }#identity-box { -moz-appearance:none !important; background: none !important; background-image: -moz-linear-gradient(rgba(255,255,255,0.3), rgba(255,255,255,0.1)) !important; border:0 !important; border-radius: 0 !important; color: #151515 !important; }.urlbar-over-link-box { background-color:#efefef !important; border-left:1px solid #B6B4AF !important; padding:0 !important; border-radius: 0 !important; }#TabsToolbar { -moz-appearance:none !important; background: none !important; background-image: -moz-linear-gradient(rgba(255,255,255,0.4), rgba(255,255,255,0.3)) !important; height:22px !important; padding: 0 !important; border:0 !important; margin: 0 !important; right:0 !important; }#TabsToolbar:first-child { border:0 !important; }.tab-throbber { /* list-style-image: url("chrome://browser/skin/places/searching_16.png") !important; */ list-style-image: url("chrome://browser/skin/tabbrowser/connecting.png") !important; margin:0 !important; margin-top:0 !important; }.tabbrowser-tab { background-image:none !important; background: none !important; border:0 !important; border-left:1px solid rgba(180,180,180,0.1) !important; border-right:1px solid rgba(30,30,30,0.1) !important; padding: 0 2px 0 3px !important; margin: 0 !important; height:22px !important; }.tabbrowser-tab:first-child { border-left:0 !important; }.tabbrowser-tab:last-child { border-right:0 !important; }.tabbrowser-tab[selected] { background: rgba(255,255,255,.3) !important; font-weight:normal !important; padding-left: 2px !important; padding-right: 1px !important; border-left-color:rgba(180,180,180,0.2) !important; border-right-color:rgba(30,30,30,0.3) !important; }.tabbrowser-tab[pinned] { padding-left: 4px !important; padding-right:4px !important; }.tabbrowser-tab .tab-icon-image { margin:0 !important; margin-top:0 !important; }.tabbrowser-tab:not([pinned]) .tab-throbber { margin-right:3px !important; margin-left:3px !important; }.tabbrowser-tab:not([pinned]) .tab-icon-image { margin-right:3px !important; margin-left:3px !important; }.tabbrowser-tab[titlechanged]:not([selected]) { background-image: -moz-linear-gradient(rgba(142,172,235,0.5), rgba(111,211,255,0.5)) !important; opacity:1.0 !important; }.statuspanel-label { -moz-appearance: none !important; background: rgba(0,0,0,.60) !important; border: 0 !important; color: rgb(255,255,255) !important; margin: 0 !important; padding: 3px 4px 3px 4px !important; border-radius: 0 !important; }