There is no extra thinking, at least for me: search on the right, URLs and history on the left. I mean: it's automatic, my fingers know what to do. I guess search engine keywords would go to the right too but I don't use that feature.
Firefox's UI is kind of all over the place, but I love that I can paste or type a search term, and then arrow-key my way down to a set of search options at the bottom.
