i see no need for a specific search engine's tool bar for Firefox at all. As of late, i've been using the Groowe search toolbar, which works with both IE and FF. This covers multiple search engines, and can be hidden or recalled with the click of a mouse. Provides all the search engine anyone would need, and doesn't clutter the display.
I use the search box, as I can either Google, or flip it down to Amazon, imdb, eBay, Wikipedia, etc., to automatically search those instead.