I had an old pair of good Yamaha outdoor speakers, as well as a an AirPort Express base station, Model No. A1084. So when I heard about the Griffin 20, it sounded like the perfect solution for hooking up my old speakers. I installed my speakers on a gazebo, ran the speaker wire, plugged in the Griffin 20, attached the AirPort Express, and then ran inside for what I thought was a few minutes to configure the AirPort Express. It turned into a complicated mess. The Airport Utility in Mountain Lion does not recognize the AirPort Express, so there is absolutely no way to configure it. I tried resetting the Airport Express, and Googled various "fixes," none of which work. I finally found a post that said that you need to download an old version of the Airport Utility that will work with the AirPort Express. I downloaded it, but then I received a notification saying that the Airport Utility cannot be installed on Mountain Lion. After 20 minutes of Googling, I found a post saying that you can install Airport Utility using a third party shareware application called Pacifist. I ran it, installed the Airport Utility, and it recognized the Airport Express Base Station. None of this is mentioned ANYWHERE on the Griffin website, and the customer support person said he had never heard this.
So how's it work? It streams music perfectly from my iMac. While my wife's iMac recognizes the Airport Express, no sound comes out of the speakers when I try to play music. As for playing music from my iPhone, it does play, but there is constant drop off. The call to Griffin was worthless, so I'm still working on this and will update this post. It will either work, and play music from my iPad/iPhone flawlessly, or it's going back. We'll see.
Update: Any type of connection difficulties are attributable to the Airport Express and your wi-fi connection. The Griffin 20 has nothing to do with it; it's an amplifier; that's all. And at $100 for 20 watts, it's overpriced. The thing that sets it apart is that it looks like an Apple product, and it's designed so that the older generation Airport Express units work with it. That being said, you can really hook up any receiver/amplifier to an Airport Express and it will play music through your old speakers. I'm now debating whether to buy a much more powerful amplifier on Amazon, for around $60, and returning this thing, but I'm leaning toward keeping it. If you get one, just be aware that Griffin's support is absolutely worthless. The guy I spoke with said he had no knowledge that the old version of the Airport Utility needed to be installed to work the old Airport Express models, or that Mountain Lion won't let you install the old version without a work around. For a company that is currently selling a device that is made for the older version Airport Express units, this is unacceptable.
3/26/2014 Update: Okay, so I've had the thing a year. I installed outside in a waterproof box I bought at Home Depot (I drilled holes so it doesn't get too hot inside). My iPhone's wi-fi reception is not great in the back yard, and it seems like that's the reason it keeps dropping the connection. Running my iPad inside works great. I've had the thing continuously on for a year without problems, including in 110 degree heat (not advised). I have to give it a thumbs up.