I've got them in both my tanks.
My 120L has good surface agitation so the airstones are completely unnecessary but I put them in at the beginning before fully understanding their purpose. They stayed because all good aquariums should have bubbles somewhere (in my head, anyway)!
My little Flex 34L is another matter entirely. I've had no end of problems with losing fish to dropsy. The shoal of CPDs I have has 2 distinct types: proper full-bodied ones and a load of scrawny ones; they are slimmer and sort of hollow bellied and it's these runts that have been giving me trouble.
The water quality is good, levels are 0, 0, 0 (Bio Nitrate-EX) and the shrimp are breeding nicely, but the runts were gasping at the top and the stronger fish were seeming listless too. The only thing I noted was that the gills on the runts were a little pink. It then occurred to me that my efforts to tame the whirlpool effect had taken away all surface movement so, out of desperation I dropped in an airstone.
24 hrs later, the tank is transformed! Fish are active and colours are better already.
I just wish I'd worked it out earlier as I could have saved two or three fish from an early grave