I had a (pink) silicone cover for my K2 and absolutely LOVED it.
It provided traction (which should be no problem with the K3 since its back is rubberized), but most importantly, it kept my Kindle pristine and completely clean
I didn't mind lending my Kindle out to family and friends because they only touched the silicone and that gave me a piece of mind.
It was very light weight and didn't bog down the Kindle in weight or look. I am getting a silicone cover for my K3 once it becomes available. I highly recommend them!