I have used ExpertFlyer to find United saver business class(IN) availability and until now have been pleased with their product. I set several alerts to notify me of IN availability in September from EWR to JNB. I just happened to look on my own and found 2 seats available on a couple of the dates I set alerts for. I made the reservation I wanted and the next day I looked at availability and United was still showing availability for both of the dates I found before (including the date I made the reservation for).
I made 2 inquires to ExpertFlyer asking why the alert had not triggered but have received no response. I am quite disappointed in ExpertFlyer, especially in their non-responsiveness to my inquiry, and I won't be able to depend on them in the future.