I'm using the AG right now (2.5 months/1.5 months of flowering), and I probably have about a month left till harvest. I only have two plants... one is huge and one is small, but I expect close to an ounce. I dunno we'll see though, but look at Dave's thread. I think he got about 56 grams or so off 3 plants using the AG, and I'm using the same supplemental fixture he's got.
As for what filthy said, I totally agree. A DIY system is much more for your buck, and if I'd known what I know now I wouldn't have bought this AG. Either way, like Tek said, it's a good learning tool and easy for those who don't know anything about growing in hydro/aero. My advice to all of you is to read up on other ppl's threads, and if you think you can pull it off, build DIY instead of throwing your money into the AG. A wise man learns from the mistakes of others, but a fool learns from mistakes of his own. Make sure you have a good understanding of what your doing before you start, and this will help your yield.
Goodluck,
WoW