They work great. I have used them for many projects. I would caution on buying from dealers on eBay. There are a lot of Chinese knockoffs. You really want the original product to keep water inside the pipe. I live in NH and have an outside faucet on my deck; the pipe is exposed to very low temps (-10 to-20F) on occasion. I drain the pipes in the fall. I emailed SharkBite about the low temp exposure and they told me they could not guarantee that it would work as water/snow could get between the fitting and the pipe and the ice could cause failure of the joint. I installed it anyway, but put caulk on exterior of all the joints to seal against water seeping in. I have had the system over 5 winters now without issue.
When using the joints, buy the deburring tool they sell and be sure that the pipe ends are smooth before making the connection