Is there any advantage to cooking beans in a pressure cooker, besides saving time?
Besides what Layne mentioned :

If you're at extreme altitudes, you may not be able to get things hot enough to cook.  A friend in Boulder, Colorado once mentioned that she can't cook beans without one.  (I don't know if that's technically "too long to be practical" or "completely impossible", though)

Also, for pressure cookers that don't release steam as they're cooking, you prevent the aromatic compounds from leaving, resulting in more flavorful food.