I tried the black rubber Incase cover and found it to be very comfortable to hold the iPhone securely but it made it impractical to stuff the iPhone into my jean pocket. The friction just prevents you from getting it out easily.
I switched to the Marware Quick Vue case
http://www.marware.com/PRODUCTS/iPhone-Cases/Quick-Vue-for-iPhone which I'm really happy with. The belt catch is secure and easy to open for taking on/off your belt, which is not true of others I tried. The case is plastic with rubberized surface with makes it easy to hold and stay clean. The open button works well. I found that iPhone is held securely inside but immediately the back left side of the iPhone would get tiny marks from the plastic ridge it rests on. I just cut a piece of a post-it note and placed it over the two ridges which is preventing the marking on the back of the iPhone case. The iPhone itself isn't getting any marks on it. I got it at the Apple store but don't see it on Apple's online store.
I see no reason for using the protective film included with the Marware case on my iPhone. The iPhone screen simply doesn't scratch with finger contact. It's like the crystal on a good watch. The Marware case includes the film if you want it and it also includes a large piece of that micro fiber cleaning cloth which works very well on the iPhone glass and your eye glasses.
Message was edited by: bosjt