How to improve... Rated 4 out of 5 stars

Great extension!
I was missing such a functionality for a long time!
But the original behaviour of the ext. did not quite fit into my Fx configuration. That's why I edited the file overlay.css which now looks like that:

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");

.tabbrowser-tabs {
-moz-binding:url("chrome://octopodtabbuttons/content/firefoxOverlay.xml#tabbrowser-tabs") !important;
}

.octopodTabButtons-button-img {
padding: 0px 0px 0px 4px;
margin-bottom: 5px;
margin-top: 1px;
margin-right: 1px;
}

.octopodTabButtons-button-img:hover {
}

.octopodTabButtons-button-img:hover:active {
padding: 2px 0px 0px 4px !important;

}

Now the ext. does not mess with my tabs (i.e. became more mild to the existing Fx configuration).