Well they keep the water moving so they are not good for fish like betta usually, depending on how powerful. If you have lots of live plants they are not good since they deprive the water of co2 for the plants but if you have few plants no problem. Basically they are fine as long as you don't have a heavily planted tank so go for it and get one.
Well what type of lighting and name how many and what type of plants you have. Usually only people who have HEAVILY planted tanks with 2wpg, co2, special substrate, and fert dosing who usually don't use airstones. I believe Gunnie or Butterfly uses them in their tanks.