As someone coming from a travel agency then they're basically a VA travel agency in a sense for flights. It's true that regular travelers do not have the knowledge (nor time nowadays) to search for cheaper fares. And by cheaper I mean not just 10 USD here/10 USD there.
I think that it's actually a pretty good idea as they can use 'hacks' (and I mean it in a good way
) that travel agencies can't. They're not tied to a GDS (which does allow some tricks though airlines do not like it) and therefore have more freedom to experiment and therefore help you save.
The service fees are OK as well considering the amount of time it must take to exhaust all the potential options and the fact that commissions are basically a thing of the past in the airline vs travel agency business (at least where I come from and I'm almost fully sure that it applies to the whole industry).
As a travel professional myself, I'm interested to give them a go at one point and see if they can beat the trusty Amadeus display