I took delivery of my ST in late 2012 and have covered just shy of 30,000km since. In that time there have been no problems worth writing about except the sat nav, which had terribly outdated maps installed. Thankfully Ford Australia were very good and provided a new SD card which resolved the issue.
Build quality has been superb with no rattles or squeaks and excellent fit and finish inside. My only gripe is with the inconsistencies between builds of the bumper to bonnet gap, which on my car is quite noticeable.
Performance from the 2L Ecoboost is excellent and I must say the engine loosened up nicely after about 5,000km. The engine note from inside the cabin is fun, thanks to the symposer, however it sounds fairly ordinary from outside.
Fuel economy is excellent with an average of 8.5L/100km over the life of the vehicle with predominantly spirited driving. On the highway you could easily see under 6 with the cruise on.
Equipment levels are good for a vehicle of this price range. I honestly can't think of anything missing at this point in time. The standard stereo is excellent with great clarity. Media connectivity works well through the stock head unit.
The ride is firm yet composed and handling is superb, however the turning circle is absolutely pitiful, I honestly don't know what Ford was thinking.
My biggest gripe with the car is the seats - they offer great lateral support, however I find them to be extremely uncomfortable to my lower back on long trips - the seats have no adjustable lumbar support to assist either. On short distances they are fine though. Having owned an XR5 previously this is a massive disappointment as the seats in it (Recaros as well) were brilliant.
Overall I do love the car and it does still manage to get a smile every time I get behind the wheel. Of Ford redesigned the seats and improved the turning circle for the next model it would be a 10.