I have had 2 Sidearmor IWB's with the J hooks for at least over 7 years. One for a Glock 27 and one for a Glock 30.
I have never had any issues with it cracking or its durability Even the rubber grommets for the retention screws are like new.....I have been a very satisfied customer. The Kydex on the Sidearmor doesnt seem to mar the finish like on some cheaper holsters like the Fobus (no flames please
) also you can easily change from J hooks to belt loops with an allen wrench. I can't speak to their customer service since I have never had to use it, but they used to have a steller reputation over at Glocktalk.com.