I have the InvisibleShield on my iPhone. It is a devil to get it on but looks very cool (or rather it is basically invisible and allows the iPhone to look cool).
It protects the device well from scratches and scuffs but I was never completely confident with it, so I added the Incase rubber holder too.
This one protects everywhere but the screen (but that's what I got the Shield for really). However the edge of the case is slightly proud of the screen so on a flat surface the screen never touches.
The Incase comes on and off in a second if required, and the iPhone can stil dock (just) with the shield on.
Not tested yet but I feel the substantial rubber will protect somewhat in the event of a fall. (

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I'm happy with this combination.