Scott McCartney, business travel columnist for the Wall Street Journal(tm) and his staff recently tested flight status alert services offered by the major airlines, the major online travel sites, and flight tracking services. Much to our delight, they concluded that FlightStats was the best of the bunch scoring points for accuracy and completeness of coverage. Many of the others fell short in surprising ways.
You can read the entire article and find out why FlightStats was the only service to attain an "excellent" rating.