a good article about it. The photo at right (not mine) shows a typical PEX connector (the brass fitting), PEX tubing (the semi-transparent tubing), cinch clamp (the silver strap around the tubing near the brass fitting), and the crimp cinch tool (the big tool working on the clamp).
I was at my brother's cabin yesterday, installing a new pressure tank for his water system. The old water tank was a teensy 2 gallon job that was mounted right on the wall, directly threaded into some copper pipe. The one I installed was a 20 gallon, floor-standing tank. We had to run about 6 feet of pipe between the old tank's mount and the new tank. If I had run copper pipe, I'd have had to cut four pieces of pipe to precisely the right length, plus three 90° elbows and two solder-to-threaded adapters for the ends. I'd have needed a box full of tools, probably five or six hours, and an enlarged cussing vocabulary to cover all the mistakes I made. Plus it would most likely have leaked the first three times I tried it.
What a difference with PEX! Because it's quite flexible, I only needed two fittings: adapters to threaded pipe at each end. I only needed one piece of pipe, and no elbows. Cutting the pipe was as easy as using a pair of scissors – the cutting tool slices right though the pipe like scissors on paper. I'd never used PEX before, so I wasn't sure how hard it would be to use the crimp cinch clamp tool. Turns out it's about as challenging as a pair of pliers. You just put the tool onto the clamp and squeeze – you're done! Then when I turned everything back on, it didn't leak a drop. Total time was about 30 minutes, and most of that was just me being careful with techniques that were new to me.
Count me as a new PEX advocate. I'm actually thinking about re-plumbing the mechanical room of our house. The current setup is an incrementally-installed copper pipe mess. I sometimes have to study the pipes for fifteen minutes just to figure out which of the maze of valves I need to turn on or off. With PEX I could easily make a manifold-based system with individual valves for every water destination...