I have and they aren't too bad to install. I purchased the wood grain one and loved it for a while. I only had an issue where they had a conductive pad that I believe picks up on the heat of your hand that you hold a finger over it and then you enter the reprogramming mode; needless to say I would accidentally hit it and wonder why my button wasn't working. But other than that they are really great kits!
I had thought about doing that but I mostly play on PC now so it isn't that prevalent of an issue since I haven't messed with the controller in a while. Plus since PlayStation now sells the back button kit for really cheap I have just used it.I know exactly what pad you are talking about. I ended up reopening the controller and removing the wire and conductive pad to prevent it from random programmer mode. I just use the L2,R2,X,Dpad_Down combo now.