I had 30-year-old copper in my house that was springing new pinholes every fall from our hard water. Partly age and conditions, partly the builder using the thinnest copper then allowed.
Doing a kitchen remodel, and since all the plumbing went next to or over the kitchen, it made sense to pull the ceiling and "wet wall" and rip it all out. It also made it easier for all the electrical changes we wanted.
I'm comfortable doing repairs in copper, and have all the tools for that but it was getting to the point that any stretch of that I had 2 or more repairs in I was replacing the whole run. I had started playing with PEX, using the stainless cinch rings. The only problem with those is the fittings go down a size, so I was going one size up on all the runs I was putting in (1/2 -> 3/4 etc.). Other than that, I like the system.
Our renovation plumber gave us a good price to replace the whole system, so we let him have the job.
It was interesting to me that he completely rethought the system layout, if I had done it myself I would have mostly followed the existing. It's still a "branch" setup, but his trunk lines didn't necessarily end up in the same places.
The other thing is, he doesn't use any kind of crimp. He uses the expander system.
Pex Expansion Tools The thing I like the most about this is the fittings have the same inside bore as the tube, no loss of pressure across the fittings. So even though most of the system he installed is smaller than the original builders' hodge-popdge, the pressure is as good or better.
So far, I am very happy with the system. Once the last of the kitchen is done, I suspect I will be even happier.