I'm about to use PEX for the first time on my hydronic heating system, which is only ~20psi and limited volume (autofill valves are an anti-pattern). Maybe I'll fall in love, who knows.
It's still relatively new compared to other pipe material, so there may be some other surprises that crop up with long term use, but I'm really impressed with its ease of installation.
Seen it a few times.
I have replaced almost all piping in my house. I used PEX-B with the fittings secured by copper rings that you crimp with the appropriate tool. It is so easy to use and confirm the joint with a gauge tool.
I had to solder copper where I couldn't replace it all. Every copper joint was it's own little project. While for PEX it's quick and easy.
Either way, my lack of confidence applies to all PEX-B and PEX-A connections. They're all essentially a straight friction fit with some hose barbs. I got some PEX-AL-PEX fittings/tube too (the 1" P-A-P has 35% larger cross section than plain PEX, and PEX larger than 1" seems rare and expensive), and the threaded compression style gives more confidence.
I'm not disputing that PEX is a whole lot easier, even knowing how to do copper and just watching PEX videos. As I said, "maybe I'll fall in love". I'm just starting with piping where a leak won't be a major hassle (hydronic, and eventually compressed air), and foresee myself continuing to do copper for any modifications to potable water in the immediate future. If I had to redo the whole house, I'd get over my reservations quick!
I purposefully avoided the stainless cinch rings. This feels like the cheapest solution to me. It has some moving pieces. I found examples of leak with stainless cinch rings online when I was choosing what technology to use. Not so much with the copper rings. The copper rings are just that. A thick copper ring that you press into shape with great force. The price of the $50 crimp tool is nothing compared to the cost and hassle of a leak down the line. Add a $30 ring cutter tool too. For when you mess up (you cannot remove the ring in place, you must cut the pipe).
I have also retrofitted the house with underfloor hydronic heating. 400m of PEX in an open loop system. Not a single leak after few years.
With the copper rings the PEX takes the shape of the fitting. Even if you manage to cut the ring. The PEX won't come off. You have to cut the pipe lengthwise to get it off. I am not sure the stainless clamps perform the same.
It's not really the pressure that has me worried, but rather the potential flow rate. I've dealt with a flooded basement before, and I'd rather not do it again.
I don't see many people complaining that PEX fails by completely pulling apart, but it's hard for my intuition to accept that.
