I have used one.....no problems thus far....very spendy....
The plumbers around here don't like them....but I could see that they might be usefull in a situation where you didn't have any PEX fittings and you needed to tap the main.....they work on PEX...CPVC...and CU....I have only installed them on CU....and they are shockingly easy to work with....
Sprinkler Solutions, Inc.
Arizona and Colorado
www.sprinklersolutions.net