I'm sure the flight hackers are aware of skyscanner, and probably know how to use it better than the average person. There are probably many exceptions like "Oh, if you're flying here skyscanner sucks and you really want to use X instead".
You don't really have a control group to know that skyscanner consistently provides the best results. It's possible that you were happy with your skyscanner experience and believe that you got the best deal, while there was an alternative that would have been much better for you. Flightfox is a relatively cheap insurance policy against that.
Flightfox is a good idea (though I'll admit I'm unconvinced computers cannot reliably beat the crowd), but it needs work on implementation.
I tried it out and the winner quoted me an incorrect itinerary cost -- didn't notice that the airline's quoted price did not include airline fees and taxes (which are in the hundreds of $$ for international flights). In the end, the true winner beat skyscanner by less than the cost of the contest.
Honestly, I find skyscanner amazing; it is the only system I know that finds airline consolidators (well flightfox does of course too) - and has a very easy to use tweaking interface.
You don't really have a control group to know that skyscanner consistently provides the best results. It's possible that you were happy with your skyscanner experience and believe that you got the best deal, while there was an alternative that would have been much better for you. Flightfox is a relatively cheap insurance policy against that.