I got one on Thursday and, due to not really having any expectations, it greatly exceeded them. And I don't even have a game for it yet.
Except I'm already having this problem where if I look at Autoplay in the 3DS Sound menu, the thing freezes, instantly. I've formatted SD cards and tried removing everything and putting it all back on. It doesn't happen if there's only one song in the root of the card but as soon as I have a folder full of stuff, the crash occurs. And this wasn't happening until today, when I had the opportunity to do a system update and took it.
I can sidestep this by simply making huge playlists and tapping things on the menu past Autoplay, getting to them from there but I'd rather be able to use Shuffle All.
Aside from that I don't really have any complaints, the 3D stuff and the AR games are really amazing. Nintendo's like the Willy Wonka of A/V technology, they essentially invent a handheld window to a world where holograms are real, and they use it as a toy. That's awesome.
Edit: The first update I tried was apparently incomplete. I did another one, fixed the problem, also added the shop. And video mode to the camera. Great, great.