Pietersen uses a bat made by Woodworm though. Obviously it wont be the same as one sold in a shop but very close to it. I've seen a video on the WW site of the owner of woodworm showing a few bats from the factory that are going to be used by KP. His bat was designed by him and the Woodworm team to give him exactly what he wanted from a bat. It will obviously be of higher quality willow and probably have bigger edges compared with the retail ones.
I personally prefer the new bats, i thought apart from the Torch that the old WW bats were quite gareish and ugly. I much prefer the darker look of the new bats, especially the Hard Drive. I'll probably go and look at a HD when they are released and will either get one of them or a Puma Ballistic Green. I am a fan of the new WW bats.