I have only used them once. I needed to go from Seattle to Delhi and I found an AF/KL/NW itinerary on CheapoAir that nobody else was displaying and came out $200 cheaper than the competition. I swallowed hard and booked it, but needn't have worried -- it came out fine, and I quickly received PNR codes that let me double-check the itinerary on all three airlines' websites. I didn't have to alter anything though.