I've used it twice. Once for a Seattle -> Berlin -> Munich -> Seattle trip. Another time for my honeymoon (Seattle -> Krabi -> Tokyo -> Seattle)

Both times I found business class tickets for not a crazy spread over coach retail and significantly below the business class prices I was finding on my own.

I've had great experiences both times. For complex / long haul flights where you want to find a cheap business class seat, I'd recommend them without question. I'm a big fan of flightfox.