I left them off. I figure I can always stick them on if the mood ever strikes me. The black surround of that rear window matches up better with the front deflector than that small deflector does anyway. Now I just need to take it in and get the tint strip on the front window. Pretty big difference in how dark the sides appear with some of the light from the windshield knocked out.
I started looking at trucks on the drive in to work this morning to see how many had put them on their rear windows. I saw more trucks with them ONLY on the rear windows than I did with only on the front.