Nitriding is an incredible firearm finish. I am a little bit crazy about finishes. IMO nitriding is way beyond anything else out there on every measure of utility. It is used heavily in Europe. To get a gun in the US with it you have to look hard or buy a European gun. I don't think it is even that expensive to do.
It is the ugliest finish though. Look at a Glock slide after it is holstered just a few times. Where it rubs the color changes. Drives some people crazy.