I just purchased mine today, and already convinced a friend to get one and another is seriously thinking about it.

I think the biggest problem with the empeg/RioCar though is that it's a niche product. Your average consumer doesn't want to remove their car stereo, plug it into their computer, and download mp3s onto it. Furthermore, this would require the user to know how to rip their CDs into MP3s too.

I think that the product could have been more successful, though, if it had been marketed to the right people. I think their biggest two audiences would be:
a) the young computer geek who loves file swapping programs and wants to listen to their illegal mp3s in their cars. They also want to have the "badass" car stereo system

but more importantly...

b) the middle-aged, middle-class hi-fi stereo junkie. I work for MUSICMATCH (mp3 jukebox software), and this is our biggest audience and exactly what Rio should have aimed for. It's the 35-50 year old white male who makes at least $50,000/yr and owns over 500 CDs. This group consists of die-hard music fans who have the money to spend on outrageous stereo systems. If Rio had gone and advertised in HiFi magazines (such as Stereophile) and gotten them to review the product, they would probably have had much better sales.

Anyways, that's my two cents.