These speakers turned out to be everything I'd hoped they'd be. Is sound quality "amazing"? Of course not, they cost ~$100. But for the price, the sound is better than I'd expected. In fact, if you plug both of them in, with the push of one button each will sense that the "other" is present to it's left or right and go into "stereo mode". Super easy.
These things pull out of the box and are ready to rock. No difficult assembly. No trouble tuning for a good signal/channel. The speakers can run off of batteries, but thus far I haven't tried them on batteries because I have AC Power on each side of my patio. They plug into standard AC power outlets and I have left-right stereo, no batteries needed.
I have another wireless stereo system built into my hot tub, but it has all sorts of problems maintaining a strong signal. If the lid of the tub lifted, or if a lot of foot traffic moved between it and the speakers, the music/radio/broadcast would often times cut out. Not these speakers. So far these guys have had very little interferece/hiccup issues with heavy traffic between the transmitter and the speaker. I'm very pleased. This also comes with all the "wires" you'll probably need to hook up to your devices to play through the speakers. A standard MP3 jack that will go into your MP3 player is built in to the transmitter, and it comes with a left-right stereo attachment that you can use if you want to take advantage of something like "audio out" on your HDTV or cable box.
They're light weight, smaller than I expected, and look pretty cool. I wish they were black, but I can deal with white. And for the money, sound quality is appropriate. Couple that with their light weight, easy use, reliable signal, and I'd highly recommend these to anyone looking for a simple, affordable, reliable solution for adding a little music to their deck/patio/backyard BBQ.
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Update: 11/27/2012
I ordered another set of these. I couldn't figure out how to order just the individual speakers, so I placed a second order for this exact product (which means I got 2 more speakers, taking my total to 4, and a second transmitter).
I am pleased to report that the two new speakers work with the old transmitter. Likewise, the old speakers work with the new transmitter. I had very little use for a second transmitter, so if I could have saved some money and only bought the speakers (in fact, I probably only wanted one extra speaker), I would have. But I now have four of these speakers that will all play throughout the house/backyard at one time, which will be nice for large family gatherings/house parties where people are spread out in multiple rooms.