If you want to hear or yourself, Gamespot have done a full review of the 3DS.
They plugged speakers in to the headphone jack of the 3DS so that we could hear the quality.
http://uk.gamespot.com/shows/today-on-the-...g=topslot;img;2
(live coverage of unboxing 3DS and testing the system) it's 1 hours 20mins long, but you can download and play it
http://uk.gamespot.com/special_feature/nin...topslot;thumb;1
Best place to go (at the moment) if you want an idea of what the 3DS is like.
QUOTE(Slyakin @ Mar 6 2011, 12:09 AM)
Gamespot fed some direct audio into their live stream, and it sounds pretty damn good.
If you don't have an MP3, it could be a viable music player. Not very useful, but it can manage.