More rust resistant and durable than blueing. Not as rust resistant and durable as Tefner(found on Glocks), Nitron(found on Sigs), Melonite(found on M&P), or Matte(found on H&Ks). It's thick and has been used on everything from knives to utility boxes for years. It generally resists scratches pretty well, but it doesn't have as good of an adherance to steel as the other gun finishes I mentioned. It can flake sometimes, just as I experienced on my SP-01 Tactical(now sold) in which a 1" section of the grip just flaked away leaving bare steel.
I think there are MUCH better finishes out there. It's better than blueing, but not by a whole lot. There are plenty of places that can give your CZ a good parkerized finish, or you can go Robar NP3/Roguard, or chrome. All of which would be quite superior. I still think Glock tefner is the best of the factory finishes..........too bad Glocks aren't my pistol of choice.
I had a P-01(now sold) refinished in NP3. A word of advice. The slide of classic CZs is thin with little gripping surface. NP3 feels like a teflon cooking pan and it will be somewhat slick. Don't put NP3 on the slide as you want a good gripping surface for a serious defensive pistol. I kinda ruined my old P-01 with that finish which just made it too slick. If I had to do it over again, I would have gone with a good parkerized finish on it, or chrome which isn't as slick.
Not sure why CZ doesn't offer blueing on all their pistols. Probably because polycoat tends to cover cosmetic imperfections, while blueing needs a good polish if you want to cover those imperfections. If you look on the inside of a CZ is has quite a bit of tool marks and the outter surface of a CZ is often rough(keeps costs down). With a polycoat finish, you don't need to really refine the outter surfaces before coating as the polycoat fills in pits and tool marks. Just a guess on my part though.
If you want something better than polycoat, check out Robar:
http://www.robarguns.com/precision_coatings.htm
They do a lot of different finishes and do fine work.