not sure about the Incipio cases for the 4 and 4S, but i have one for my iPhone 5. i bought it from an AT&T store. i love it. it's not too hard. it doesn't have to be forced on. it doesn't snap on. it's the perfect mix of soft yet sturdy. it's easy to pop off and on when i want to clean away and lint or anything from my phone.
i've had my Incipio on my iPhone 5 for about 1.5 months now and there isn't a single scratch around the edges like i've seen with other cases that rub against your phones antenna.