I didn't buy this specifically for a DSi, so my review is directed to potential buyers looking for a tiny powered speaker for other uses.
This thing has very thin sound. It's equivelent to a cell phone speaker. There are no lower frequencies coming out of it at all.
I also bought the Fidelity Mist Plus portable speaker on amazon. It's about the same size and weight, and costs less. In terms of sound, it completely blows this thing away and really defies expectations based on the tiny size. If you're looking for a pocketable powered speaker that's cheap, that's the one to get. It comes in several colors too.