I agree with Grawr on everthing he's said.
As for the DSi, I don't see the point of it. Camera's? Useless. What kind of gaming handheld needs a goddamn camera? Very bad quality ones at that. Remove the GBA slot for an SD card slot? Stupid. I prefer to play GBA games. Ability to listen to music? That's what an mp3 player's for. All for the low, low cost of $170. Save your money, keep your DS and just buy other things with that money. Hell, you could buy an mp3 player with more space and a decent quality camera for that much.