Slows Firefox down. Avoid. Rated 1 out of 5 stars
Used to be great before 'Plus', now it slows Firefox horrendously for a few minutes after you start it up and, although AdBlock seems to catch them, tries to deliver adverts. Still can't understand why exactly what this does isn't a native feature in Firefox.
If you're looking for something that gives you more than one row of bookmarks, leave this page and look for 'Roomy Bookmarks Toolbar' instead. It does the same stuff, but better.