[DEinspanjer]

I greatly prefer being able to hit enter on the first result too. Here is the addon I use to enable that: https://addons.mozilla.org/en-US/firefox/addon/mozilla-labs-...

[bad_user]

You don't need an addon -- the option is in about:config.

[waterhouse]

Specifically, browser.urlbar.autoFill. (Found that out just now.)