I used their titanium recoil spring guide rod on my G23. I also used their extended slide release on the G23. I made these purchases way back in 1994 (IIRC). They are both is still on the gun today.
My only problem with the guide rod is that it captures the spring. At the time was not a big deal to me, but as I have learned more about guns, I wouldn't make that purchase again.
I think the need to change out springs is pretty important for a heavy use gun. And at a cost of somewhere around $32 for the guide rod, I don't want to make that purchase every couple of years. With somewhere around 6,000 rounds through the gun since then, I need to change it out.
As for the slide release, it has served me well over the years, and just recently began to get a little surface rust. It was actually my fault, but still. I wet down a new leather holster, to enable better fitting (I know now it isn't a good idea...plastic baggy trick seems to work better). When I retreived the gun in the morning it had surface rust on the slide release. It cleaned up fine, and I will have to get it refinished eventually.