The protector really could save your controller if you smash it into a wall etc. Hell, it could even partially help protect your human hands if, like *ahem* some of the more clumsy members of our staff, you're liable to smash those too. The plastic is strong enough that we can't imagine breaking it unless you intentionally set out to do it.
While the product is not difficult to install, it requires a certain amount of force and doesn't seem to achieve an absolutely perfect fit. As the protector ring mounts around the sensors in the Touch controller, it may also occasionally block signals at certain angles.
If your home is filled with violent children, or if you are particularly concerned about protecting your Touch controllers for any other reason, this product will do the job. But it's probably dispensable for many users.