Update 12/21/08: Firefox Refusal of the "RichResults" to obey the "Clear Private Data" command and how to disable RichResults feature.

While at this time there is no way to make the Location bar behave exactly like in Firefox 2 there are several experimental add-ons which received good marks from the users. (Experimental add-ons may be alpha, beta or pre-production in quality, performance and features. Caution should be used when installing experimental add-ons, as some of them have not been tested by an editor and may harm your computer configuration.)

Clear Private Data... (Add-Ons) 0.2.2

This extension utilizes the "Clear Private Data..." feature that is part of Firefox version 1.5 and above. It makes this feature a lot more accessible via right-click context menu and an optional toolbar button.

Homepage: https://addons.mozilla.org/en-US/firefox/addon/1280

Hide Unvisited 3

Hide pages (bookmarks) that you haven't visited from showing in the AwesomeBar. This is for users that don't want to see any bookmarks showing up unless they've used the bookmark since deleting certain pages/sites or clearing the history.

Homepage: https://addons.mozilla.org/en-US/firefox/addon/7429

Old Location Bar

If you like the look of Firefox 2 Location Bar. You will not be able to completely back to the Old Location Bar but there a few features listed: URL Bar displays the old way; Go Button is always present, only matches what you type, doesn't guess; and URL Bar turns Yellow when visiting a "Secure" page.

Homepage: https://addons.mozilla.org/en-US/firefox/addon/763