I do a good amount of plumbing work and the Shark fittings definitely speed up my repairs or changes to lines. There's also the benefit of not having to take precautions when soldering close to wood or other flammable sources. I like the single stop unions that allow you to cut into a line to make changes or replace a leaky fitting. Just slide the non-stopped end onto one side, then slide it back to join the two pipes without having to flex them to get a sweat fitting on. When working with those fittings and copper pipe, I always remove the bushings from both sides on the inside of the Sharkbite fitting. (Those are usually loose and rattling around so take a needle nose plier to pull them out). When I've left them in place, they sometimes jamb up the copper pipe from being inserted fully and they're only needed for CPVC pipe. Make sure that there are no rough spots or burrs on the copper pipe or you'll groove the fitting seal and possibly create a leak.
I spoke with the owner of the company quite a while ago praising the fittings, but also making one suggestion. I also use their ball valves, but hate how they spin once connected (the handle will rotate with the fitting 360 degrees). He told me they were working on a design to form a keyway to keep it from rotating.
I've been using them for a few years without any issues or call backs. Just make sure you mark your pipes with a black marker, for the depth the fitting is supposed to go. That way you're sure that you have full insertion of both pipes into the fitting. It can be hard to tell, until you turn the water on!
I also love how easy it is to use the keys to quickly take a Shark fitting apart without having to de-solder/solder.