They are code approved to be behind walls.
But some people are still leery of them.
They have an excellent record, as long as properly installed.
They are expensive, but can be much faster and easier than soldering in lots of situations.
Make clean pipe cuts, straight across, no burrs or nicks, clean the pipe that goes into the Sharkbite, and insert fully by marking the correct depth with a little gentle scratch or a Sharpie.
They rely on an o-ring seal, and teeth that grab the pipe must be properly seated.
They are not suitable for any connection that must be rigid.
They are not meant to bear much weight or resist spinning or turning.
They will rotate, which is not good like for attaching a valve with a rotating handle.
Unless you can stabilize the valve by screwing it down or otherwise holding it from rotating.
If I need to work somewhere that soldering will be difficult or dangerous, but I need strong mechanical support, I use regular wrench type compression fittings or couplings.
Also, ProPress fittings are great but need special expensive tools to squeeze them on.