PEX is now nearly 50-years old, it's been in use in Europe for longer than here. There are literally billions of feet of the stuff run. In a repipe, it's certainly easier to use, and ease comes with saving some money - labor is not cheap! Because it bends, you can make runs with few or no fittings except at the ends or transition. Because it bends, you need to use the right stuff to transition to shutoff valves, or things that previously might have relied on the plumbing to hold them in place. Good practice calls for transitioning to copper stubouts and anchoring them well. The OD of pex is the same as its copper equivalent, but the tubing thickness is greater, so the same sized pipe can't carry as much volume (don't confuse volume with pressure). So, you may need larger pex than the pipe it replaced. There are three different manufacturing techniques with pex, labeled -A, -B, and -C. -A is often the most expensive, can be bent into the smallest bend, is the most flexible, and is the only one that can be repaired if it gets kinked...the others, -B and -C when kinked, need to have that section cut out and a fitting installed. Kinks aren't that frequent, but that depends on your technique. There are two general methods of attaching fittings - an expansion type and a compression type. On the expansion type, you slide a reinforcing band around the end of the pipe, insert a special tool, expand the whole end of the pipe, then insert the fitting. The pipe has memory, and collapses around the fitting, making the connection. The other type, you insert the fitting, then use a tool to crimp a retaining ring on. Because the fitting's OD can't be as large as the one that you expand to make it fit in the pipe, this type has a slightly smaller hole, thus slightly less volume capacity. The only one that can use the expansion fittings is (to my knowledge anyway) -A, and Uphonor (Wirsbo), one of the original manufacturers of the stuff, makes it that way (there may be others that make -A). Short answer, done right, PEX will save some money and last a very long time.