Do side by side comparisons. I haven't seen any of my searches (admittedly only the few I checked for this) differ from Bing's results in results or result positioning
It's unfortunate really as the owner guy keeps saying they use multiple sources but in all of my tests.. they're all Bing. I don't care about using Bing, I do care about being deceived (slippery slope, thin end of the wedge, etc etc)