For what it's worth, I tried this procedure (to make the a,b-unsaturated ketone though, not for benzylic oxidation) and it didn't work at all. A lot of that could be due to my technique though, I certainly wasn't experienced with those types of reactions, but the IBX I used was pure and it still didn't work. I say try the lower grade stuff (especially since they say they did). If I'm not mistaken, IBX is fairly inexpensive, it's DMP that really starts to hurt your pocketbook.