It's a great option to have and I appreciate the added features to interact with music. I'm sure people with no other options (namely a younger croud) will get value out of it.
I've an iPhone 4 for all of my media. Photos, music, videos, news, etc. I have solid games too, but they can't hold a candle to a dedicated gaming device.
In short, no, I don't use 3DS Sound but I'm glad they included it (and also that the headphone jack is now in the middle of the system! Good call!)