Apple's Safari has a nice way of handling gregtrainer's problem of having his search keywords clobbered by an engine's URL, but in keeping with current one-text-box browser UI.
if you type a search phrase into Safari's address bar that is searched with the default engine, Safari simply keeps the search keywords displayed and does not show the actual URL. then you can just hit Cmd+L and type more words when you need to narrow down your results.
Safari's behavior really makes sense to me, as I hardly ever need to manually copy a search engine link, but am almost always refining search results. And you can still click a bookmark or share button if you do need the engine's URL.
I even have DuckDuckGo configured to not waste space on displaying its search bar in the page header because of this feature in Safari.
I'd sure like Opera to implement this too