I have one. I tried the lettuce first an it grew phenomenally fast and looked impressive, but it was a soft and wimpy lettuce which wasn't much fun to eat. Then I tried one of the mixed herb kits and had mixed success. I finally tried the international basil kit and it was a hit. I had so much basil that I gave loads away.
In my personal opinion, if you have the space and time to grow a few things outside then you are probably better off. Otherwise, it's an interesting gadget and could be handy in the winter. I don't know if it will pay for itself, but yesterday I paid 4 bucks for a small baggie of basil and think I'll buy another basil kit and plug it back up
Btw, Amazon has a wide variety of aerogarden kits at good prices.