I wouldn't use the camera. The DSi has internet and the DSi shop. I'm guessing the hinges on the DSi break easier because of the added wieght on the top. So a gaming system with DSi shop, that has a slightly bigger screen and stylus with internet, much more costly and less battery time, the newer ediion. I would rather have a DSi than a DS lite if they were free, but the cost is too much, and the new features really aren't worth it to me.
I didn't think it was a fail. Just a slightly smaller version of the GBA. If you didn't already have a GBA back when there wasn't DS, I would get that instead of GBA. The GB Micro isn't fail, but it isn't a nescasary addition to portable gaming.
A DS can do all the things a DSi can do, except for two things: DSi specific games and use cameras.
A DS can do the same thing, go on the internet. Just buy the Opera Internet browser...
And I don't think you want to listen to music with the DSi... crappiest speakers ever. Though you could use headphones, but then again you can do that with anything... cellphone, iPod, mp3 player... lots of stuff.