When we moved into our house in 2009 there was no shutoff on the sillcock. House was plumbed up with pex which at that time I had no experience with. It was super simple to put in and so far has not shown any signs of leakage.
We have started to carry them in the work trucks incase we hit an unmarked water line with the trencher. Cut the line off flush, slip the sharkbite valve onto it.