I also have used a Ursack for a decade, and have not had a problem. However, I'd absolutely NOT hang them, as in bear-bagging. The bear, familiar with bear-bagging, will specifically target the bag, wheras if they are able to inspect it, they will get frustrated and leave. I do like to tie it to a dead tree.
Of course, they can only be used in areas not requiring cannisters, but they also work against mice, marmots, etc. I think in areas that they are required, the bears are "educated", and will spend hours and hours on them, where wild bears will not.