The pro's are accuracy, low noise, non-existant recoil, and in most cases, fairly inexpensive rifles. They extend your rimfire range to about 120 - 150 yards. The con's are you can't wipe the grin off your face - and (the real bad part) you can't find the ammo right now!!!
Cost is about the same as reloading a 22-250 or .223 only you don't have to do said reloading.
It's a fun little round.
Skein