I'm going to disagree a bit here. I'm not saying that an Ursack isn't safe from critters. But I think even if I had one I would hang it.

For me the issue is one of peace and quiet as much as anything. If I spend all night listening to critters ATTEMPT to get into an Ursack then I still lose a night's sleep even if I don't lose any food.

Sound sleepers may not have this problem. I'm a light sleeper and for me a raccoon messing around in my camp can really ruin my sleep, even if he goes away hungry.