I did encounter this weird screw-up:
This only happens because I have "large fonts" set on my computer. The real problem here is it took me a while to realize what the combo box said (since I don't like the icons in the default theme, I really wanted to switch to text), since I could only see the top half of the word "Icons".
The clusterfuck is that the scrollbars in there are a hack on a hack trying and failing to fix it; you can read the bug report (now 1.5 years old!) here, which includes ranting about "why are we still wasting our time on using this goofy non-standard UI widget given that it's been broken for a year" (paraphrased).
UPDATE: One annoyance I've discovered is that the 'Go' menu doesn't work to navigate you back in your history stack. This is because of tabs--all pages you've visited in any tab goes onto the go history, so clicking on an entry in it can't send you back there without mucking with all your tabs; it just goes there on your current tab, pushing it (again) to the top of the history stack. Of course, jumping back to the old point in the stack is exactly what the old non-tabbed browsers (NS4, IE, and apparently Mozilla too) do, so this menu totally fails to let me make use of my tree-structured depth-first-search model of searching the web, even though I'm not using any tabs! Apparently the right-click context menus on the back and forward buttons (what, they have right click menus?! of course this isn't documented anywhere, and the Mozilla forums don't allow you to search for the word 'go', for no apparent reason) behave in the old, tab-relative way, but 'Go' does not, so the solution is to download an extension that lets me get rid of the Go menu entirely until I retrain my muscle memory to use the right-context menu instead. Grf.