I bought the Cowon M2 for the reputed sound quality, the provision of a microSD slot, and the extended battery life. The sound quality is excellent and, for me, far outweighs any of the shortcomings in the GUI and touchscreen. I have been unable to t...Read morehoroughly test the battery life, but using it for about 20 hours seems to have made no impact on the battery whatsoever, so it is already a huge improvement on any media player I've used before.
I have no reservations about the sonic performance. I have been listening with B&W C5s and Grado SR 60i and the results are a delight.
As others have said, the touchscreen is a bit fiddly and the GUI is not quite as intuitive as I would have liked. However, after a day or two of use, it now feels like I've got the hang of it.
In summary: if you're interested in listening to entire albums in high fidelity sound, then this is for you; if you're likely to be looking for and playing lots of different tracks, then you may find the interface a bit frustrating.