I have a 2007 fiesta, which is of course much older, but I would imagine the ecu etc probably uses the same calculations or whatever.
The distance to empty is pretty accurate - with a few caveats.
The fuel sensor/ecu will quickly respond to a perceived drop in fuel level, but take much longer to respond to an increase. Example - driving along on a straight road DTE reads x, come to a roundabout the fuel sloshes around and the DTE starts to plumit. Stays low for the rest of the journey, but park up and come back half an hour later and DTE has jumped back up again.
I regularly drive on almost empty to save weight, and when this low on fuel even filling up at the pump it won't update until the ecu has been to sleep and reawoken.
Once I got cocky - car had been sitting overnight on level ground (very important!) showed a genuine 2 miles to empty. Cheapest fuel was 4 miles away - no bother, these things are always over cautious anyway... the last mile was walked with a jerry can in hand
As long as I start my journey with enough miles to go showing, I know I'll be good.