I've replaced a lot of my system with PEX. I totally re-did the area where the
pump and water
heater are. I haven't replaced the lines to
remote fixtures; so far they
work fine.
I went with "shark bite" (or similar brand) press-on connectors and fittings, on the theory that they're easy to remove and re-install without tools. For some reason I seem to need to do this more often on a boat than I ever did on my house.
That said, these fittings are more expensive, and removing them isn't always as simple as you'd think, if they're in a tight location or there's not much room between fittings.
For the house, I bought the PEX ring
compressor tool for a small job, and I'm liking this method a lot. Easy one-handed install, and
removal isn't too hard; just replace that section of PEX. It's
cheap enough not to bother re-using the old section.
If I had it to do over, I'd use the shark bite connectors where I thought I might need to someday pull the connection apart, and the
compression rings on the rest. The tool isn't that expensive, and probably cheaper than
buying all those shark bite fittings.