To answer the OP, they are absolutely perfect for all critters other than bears. I have pretty much used one (the SAME one – Kevlar material, no special "lining")on every non-bear-can trip I have made in the past decade. As for critter experiences, tons. My ursack as numerous battle scars – none of which decrease its functionality a jot. I'd say most places where I know there are no bears and am too lazy to suspend it as opposed to hanging it on a branch it would be the exception NOT to find some critter action overnight. Racoons are the most persistent buggers, and if given a comfortable place to sit, can get a tooth in between the strands of Kevlar leaving a "pin hole". Same with mice. I have also seen skunks and possum. But I sure I've missed seeing about %99.0 of them at night when the action goes down. Ive had a flock of Turkeys peck at it one morning in Henry Coe.
So my ursack is on my gear list most of the time when bears are not present. Protects my food inviolate – tested on real animals.
The critters (including bears) can absolutely NOT rip the Kevlar. If they work really hard bears the CAN make a hole between the fibers. I know the seams might get ripped by a bear with time on his hand and no distractions.
Whether or not the ursack "works" with bears depend on you point of view. The ones in the picture were NOT used as per instructions. One central idea for both critter and bear is not to tie the bag anywhere the critter can sit for a long time and chew comfortably. Read the instructions. Also, and its probably just me, but I would never fully trust anyone that took that much commercial packaging on a backpacking trip. ;-)
Secondly, and this is absolutely clear, the Ursack, when used to keep a bear out is NOT intended to protect your food – its purpose is to protect the bear from your food, and that is the only criteria Yosemite and the other parks care about. Again, regulations are not about you, they are about the bear. At any rate, it was eventually realized that a patient bear could pulverize you food into a paste and eventually squeeze it out of the bag like toothpaste, even without an actual "failure" of the bag. So no ursacks in areas of high bear-human contact.
Summary – great for protecting your food from non-bear critter bandits. The guys with small mouths will not usually do any significant crunching of the food inside either. Ursacks need to be tied correctly with the Kevlar cords – ideally to a branch that make it hard for a critter to relax and have at it. In places where you can hang, learn to hang correctly, and then the Ursack is superfluous. In places where it is legal in bear country, and you can't or choose not to hang, know that the bear will turn your entire food supply in to mush chewing on the bag if it gets a chance. As mention above, if you are going to use the Ursack like that know that you will need to be prepared to scare the bear off it, and that is likely to be a night long task.
Personally I'd never use one in bear country – I bring a can, or be prepared to hang – correctly.