Press [Enter] in the AwesomeBar to select the first result, which will be automatically highlighted. This saves you from pressing [Down] or [Tab] before pressing [Enter] to select the first result.
Example: typing "enter selects add on" then pressing [Enter] will bring you to this page. This differs from autoFill which only tries to complete some URLs (and it never works when matching titles or multiple words).
The add-on will try to be smart so that when you're typing in a url or a site.com or site.org, it'll go to what you typed in instead of the first result.
To edit or go to the inline-autocomplete url, press [Up] to deselect the first result and return to the original completion.