The Eton rukus is a well made boombox with the key feature of having a solar panel to charge the battery. Unfortunately, it seems most of the product cost is going to the battery and solar panel rather than the speakers themselves.
The sound from this unit is ok, but not great. You'll get sound similar to lower priced systems, but you do get the added benefit of a long lasting battery and the solar charger. The speakers are two small full range drivers. They are not ported at all, and their positioning makes the sound come out in a pretty directional nature.
The volume can be controlled on the unit or by your device. Cranking it all the way up, it's not all that loud for filling a noisy room or playing to a crowd outside. That said, the distortion isn't all that bad, either. What it lacks in sound, it makes up for in portability. The handle and design of the unit is very good quality. It feels sturdy.
I like that the elastic band to hold your music player is recessed and protected, although the down side to this is that it's on the underside of the Rukus, and you can't see it unless you take it back out. Therefore, you pretty much have to be resigned to set a playlist then walk away. Since it's bluetooth, there's no way to skip/reverse/pause from the unit. The only sound customization is a "bass" button, which adds a little, but unfortunately there's no indicator on the screen to let you know if it's on or off.
The e-ink screen is good, no complaints and when it changes, it doesn't flash completely black like some ereaders. It simply updates. Unfortunately it only displays battery level and the input (USB, Line in, or Bluetooth). It does not indicate volume or if the bass boost is turned on. I really would have liked those to be displayed.
In all, if you want something portable and solar powered, this would be an ok choice, just realize you're spending some of your money on those features vs. sound quality.
[Update]
Just wanted to update this review with a few more observations. The Rukus doesn't really charge via the solar panel while indoors. If it does, it's not strong enough for the charge indicator to come on. It will charge outdoors, even in fairly overcast skies.
Another good use for the Rukus is that it can charge any device via the USB port. To do this, you have to have the unit turned on, then you have to press the USB button. It will still play via bluetooth, but just plugging something into the USB port doesn't automatically start charging it. This makes sense in that you might not want to drain the Rukus' battery every time something gets plugged into the USB port. This also makes the Rukus a choice for disaster preparedness, travel (like mission trips or when you're not sure when you'll have power available), etc.
Lastly, I'm still not overly impressed with the sound. It's ok, but not on par with other docks. I believe that the size of the speakers and volume limitations are probably a design choice that helps conserve battery life. Driving bigger speakers louder would certainly take more power thus reducing the length of time you can play on battery power. I do like how it can be laid flat or be stood on end. By standing on end indoors, it helps disperse the sound as it hits the ceiling.
[Update #2]
I used this as an iPhone charger at a baseball game. My phone was about 50-75% depleted and the Rukus had about 3/4 of its battery left. I was using a baseball scoring app that drains the battery pretty quickly. It was bright and sunny and the Rukus was in direct sunlight. I was just able to get a 100% charge before the Rukus' battery was completely drained. Once drained, it shuts off. I guess the point is that if your iPhone needs charging and you plan to have it on using apps, it will drain the Rukus faster than the solar panel will charge it. I thought this might be useful info for some people.
[Update 7/2012]
In my quest to be green I placed the Rukus outside to charge the battery, then forgot about it. It rained. Now water is clearly inside the unit as the solar panel is fogged up. I'm trying to let it dry out before powering back on. Lesson learned: it's not water resistant. Not sure if I will let it dry out on its own or try to open it up to dry out.
Also, the plexiglas panel covering the solar panel is easily scratched. I took it to a baseball game (very dusty) and was placing a cooler and my drink on it since it provided a nice flat surface. Now there's a bunch of fine scratches on it. Doesn't seem to affect anything other than aesthetics, though.