I have had this device for maybe half a year now and whilst I was originally impressed with it, I have become less so over time. Initially, my laptop had problems interacting with it as there wasn't obviously any driver but after having installed Rockbox it works fine and I'm able to drag and drop files from my computer onto the device with ease. I didn't spend much time with the Sansa firmware but the time I have spent I had trouble navigating and I couldn't find any way to use the external memory (though I didn't spend much time on it).
 
The reason for wanting the device is because the two HTC mobiles I own both have piss poor sound quality; bloated bass and hissing/pops/squeaks during quiet parts of the track just make for an unpleasant listening experience. I was pretty much sold by the supposedly black background, flat frequency response and high SQ to price ratio and but have found it mediocre at best. There's no particular emphasis on any frequencies as far as I can tell but there is a lot of noise when scrolling and during tracks for no apparent reason. The buttons feel cheap and there isn't much weight to the device which leaves it feeling a little like those toy mobile phones you can buy at cheap novelty toy shops. The screen scratches easily and it doesn't feel very durable at all.
 
It offers good value for money with wide support for different audio formats but it's not without its faults.