I put one in my 29-gal. From what I understand it's truly personal preference. They add oxygen to the water, which is a benefit, but alot of people don't like the additional noise (doesn't bother me, though). I've also noticed my fish playing in the bubbles - it's really cute!
To run one, you need an air pump, air hose, and whatever bubble wall/airstone accessory you choose. You should also get a check valve to make sure no water can back up into the line and get in the air pump.
To others with more experience - am I forgetting anything?