Pros and Cons
Pretty good overview:
Negative View - But Conclusion is That they Work Well
In the video above - this plumber explains why he doesn't use them - citing higher potential for leaks: Video comments:
- One Australian plumber says everyone uses them in Australia and if they don't, their work costs too much and thus they are not competitive.
- Comments also say 'The bottom line is that the independent testing has said "Sharkbites work, they work well, and they are no more likely to leak than other fittings!"'
- 'This sounds like plumbers talking bad on sharkbite because it makes plumbers obsolete...Quickest and easiest way to connect. I know it sucks when your trade is being undercut by an invention but don't be that guy.'
- Push-fit leak more - 
- Stay away from push-fit, but clear reason is not given 
- Reliable but soldering is better 
- Sharkbite says PEX lasts longer than copper 
- M type copper lasts 20, L type lasts 50, and K type lasts 100 
- PEX will likely last as long as copper.