Useful post for tweaking your toolbar layout and styles in Opera. I didn’t know about this particular file (toolbar.ini) and the extent of customization you can achieve until I read this.
My current favourite tweak from the post: removing button outlines from the extensions toolbar à-la Chrome. Personally, I thought they looked slightly icky. To do that, close Opera and add this to your Opera toolbar.ini file:
;Button skin=Extension Button Skin