Haven't gone yet, but booked a cruise on Viking Ocean for July 2019 through Cruise Compete. No OBC, but a substantial savings from what the price was on their website. I spoke to the agent prior to booking (Cruise Vacation Outlets) and she was extremely helpful. Viking is known to require payment in full a long time before the cruise, and she was able to shorten it to 6 months prior. Then, I had to deviate on the air, and again very happy. Within minutes she emailed me an updated invoice.
Hopefully, I will be just as pleased next summer