I used one thisApril (electronic version though) for coastal brown bears on Afognak Island. I did get the chance to see how it affected a sow with cubs, she scooped em up and got away, but it never did bring in a boar.
Made 3 set-ups last season and used the distressed cub call, no luck and we were in an area with lots of fresh bear sign, I've talked to 2 different varmint hunters that told me they had bears come in to their distressed rabbit call.