Had an Incase silicone, but it got stretched at the sides and was difficult to slide in and out of my pocket. On the plus side, I could set it on the car dashboard or the leather seats and it stayed put. Also, the few times I dropped my iPhone it was well cushioned.
Just replaced it with a frogz slider (red). I love the new look, it's easier to slide out of pocket, and it won't stretch. It's a little more grippy than a naked iPhone, but not as much as silicone. Drop protection remains to be seen.
So far, I am happy with the frogz slider.