I cook beans quite frequently, and typically soak them overnight then cook them the next day. I don't find that particularly laborious, so I've always wondered why people use pressure cookers. Are there any other advantages besides the time they save?
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.
Pressure cooking requires much less water than conventional boiling, so food can be ready sooner. Less energy is required than that of boiling, steaming, or oven cooking.
Because of this, vitamins and minerals are not leached (dissolved) away by water, as they would be if food were boiled in large amounts of water. Due to the shorter cooking time, vitamins are preserved relatively well during pressure cooking.
Not only is this steam energy transmitted quickly to food, it is also transmitted rapidly to any micro-organisms that are present, easily killing even the deadliest types that are able to survive at the boiling point. Because of this enhanced germ killing ability, a pressure cooker can be used as an effective sterilizer for jam pots, glass baby bottles, or for water while camping.