I recently received a new SL-C1000 from eBay. I had read on different aspects of this machine (hardware, roms, apps, etc) in this forum here for a while, for which I thank the forum administrators and everyone else on the forum.
One of the things that was somewhat important for me was to have in the SL-C1000 a good substitute for an MP3 player. I've been using an iAudio G3 for a year now, and being one of the players with better audio quality, I'm a little bit spoilt. That's why I had some reservations about the sound quality on Zaurii. This was reinforced by several threads in which the sound quality of these devices was questioned (although often with qualifications such as: "the sound quality is very crisp, but the bass is awefully lacking", etc.) I am aware that sound quality is very subjective (just take a look at forums like head-fi.org and you'll know what I mean), but still I was not sure of what to expect.
I finally gathered the courage, and dumped a good rip of Close Encounters of the Third Kind (John Williams) on an SD card, and loaded it on the Zaurus, which I had connected to my Sony MDR-7506 headphones. The first impressions were excellent: Clear sound, with good separation, and perfectly balanced bass. I had perhaps set my expectations too low, but I have to say I was impressed.
After some more listening time, I still like the Zaurus very much, and I must say it will replace my iAudio G3 as my main mp3 player. I don't think the quality is as high as the G3, but it is so close that the deficit (if real and not imagined, which is also possible) is so small that it is not even worth considering.
That being said, I understand why people would comment negatively about the lack of native software with a working EQ (which I believe the Quasar player has resolved anyway.) I personally like to play without EQ, because I think that if the source is good and all the elements of the audio chain are doing their job correctly, there shouldn't be anything in the sound to change.
If anyone has considered a Zaurus (I can only personally vouch for the SL-C1000) to use as an MP3 player but has been put off by third party comments, don't be concerned. It's very good!