For a few months now I have used The Flight Tracker. It worked fine most of the time, but some weeks ago there was that one flight that got totally messed up. At first, the flight got more and more delayed. When the delay reached 5 hours the flight was cancelled. The Flight Tracker, at first, showed the delays, but later reported that cancelled flight as having operated on time.
That same flight, on FlightStats, was reported correctly. Thus, I am very eager to see how FlightStatus will behave in case of operational irregularities.