Soon, very soon, the Firefox devs will ship Firefox with a UI that doesn't require tweaking to not look like complete ass. I have great hope for them. Until then, there's always tweaking ~/.mozilla/firefox/[profile]/chrome/userChrome.css:
toolbar{
height: 32px;
margin-top: 0px;
overflow: hidden;
}
I have to use this little tweak on my desktop to keep the Stumbleupon buttons from taking up 48-64 pixels, depending on whether it's Thursday and the SU crew have 'fixed' anything recently. Thankfully, the Mozilla team have a pretty decent documentation of userChrome.css.
