I bought an Incipio case from the AT&T store, at the suggestion of the sales associate who owns an iPhone.
The phone protector comes with:
1) A rubber shell that covers the whole phone, minus the screen, camera, headphone jack, silent switch and charging plug.
2) A hard shell that snaps onto the back of the phone, covering the rubber protector. The rubber protector is formed so the two pieces join perfectly... there's no raised areas once the back hard pieces is attached.
3) A screen protector that doesn't use glue, but sticks to the screen very well. If need be, you can remove the screen protector, wash both sides of it with soap and water and put it back on and it sticks just as good as new. If you didn't know better, you'd think there was in fact glue on the back side of it.
4) A cloth to safely wipe off the iPhone screen.
If you look at the third image, you'll see the hard plastic piece that attaches to the back. Their is a square in the middle, and the 4 side areas that the hard plastic does not cover. This makes it easy to hold onto the phone, since rubber is still in key areas, but also makes it so you can slide it into your pocket since most of the back is smooth, hard plastic.
The package I bought at the AT&T store came with 1 clear hard plastic backing and 2 rubber pieces; one black and one white.
I'm glad I plunked down the money for this phone case, seems to protect my phone pretty good. I slide the phone into my pocket with the screen facing me, so the hard plastic is facing out, just in case I'm stupid enough to walk into something or fall down.
EDIT: Oh yeah, forgot to mention that the hard plastic piece snaps on by going over the corners... you can see this in the photos... so if you drop the phone and it lands on a corner, you're still good. Screen protector is crystal clear too, once installed properly (no dirt or lint under it), you can't even tell there's a screen protector on it.