It always works - the failure rate is zero. Inconvenience compared to breastfeeding. A bottle feeding mother needs a fair amount of additional equipment, a breastfeeder comes equipped from the factory. Some babies don't tolerate formulas well because of milk allergy or other milk sensitivities. This can be to both types of ordinary formula, cow milk or soy.
Cost is considerable compared to breast.
Generally, more gas and air swallowing problems with artificial nipples than mother's nipple. If you have the nipple on too tight, the suction that quickly forms in the bottle will stop the milk flow, the nipple will collapse, and the baby will swallow a lot of air. Just tight enough so that the bottle doesn't leak, no tighter. I am skeptical about them as opposed to simply loosening the nipple, but have at them if you are so inclined. Keep the child as upright as possible during the feeding.