I want to do it, and was wondering if anyone has done it. I know it will look glossy, and I'm thinking that would be kind of cool. If you have, put a pic or two up so we can see what it looks like.
my zagg backing is matt.....but I have a white lumia and it gets all dirty around the edges in a few days and looks horrible on white so I just kept the screen side on.
I just put one on yesterday. I also had one on my black Lumia 900 as well. Makes the phone look glossy, but its a lot grippier. I don't have any pics but I got the full body kit.
Is it necessary? No, but I had noticed a couple very faint scratches on my screen so I figured why not just in case.
I've just purchased a Gadgetshieldz cover for mine. Same as Zagg but cheaper. I had one on my Lumia 800 and it was excellent. Stopped it slipping out of my hand as I always found the back to be slippy due to the matt finish.