The Penntek Power Pull isn’t a bad product. It just functions just like a modern normal hammer in every respect, except for the pin. The Power Pull does offer a leverage advantage when pulling larger nails, but not a significant one. You’d probably be better off practicing driving nails well so you don’t need to pull them back out — or just pull them out with the hammer in standard mode.
Street pricing runs about $35 plus shipping. That’s as much as top-of-the-line hammers in its class, so you’d better be sure you’re willing to pay such a premium for the pin.