What about the Lite and DSi? From what I'm seeing, the only reason people are buying it is the fact that it has a camera, and little add ons. Is a camera and a few little extra features (some that cost additional money) worth $60 more than a DS Lite? I say no, though some would argue. A lot of people who buy the DSi just for the features that the DS Lite doesn't have probably have a phone. And that cell phone probably has a camera. If you look at the capabilities of the DSi phone, it's only 0.3 mega pixels, and the resolution isn't that fantastic coupled with that. Basically similar to a camera phone. The only instance you will need the DSi phone is if you need to take a casual picture, don't have a better phone, and don't have a camera phone with you. Some people will find an instance like this, though the DSi phone won't be replacing a digital or even traditional camera any time soon.
The added features? They do make the DSi more of a multimedia electronic. There are quite a few people who don't have their own MP3 players like iPods or Zunes or the such (namely myself). I expect that the audio capabilities are lower than the former though, so the DSi won't be replacing MP3 players any time soon either. Useful for a pseudo player though. The feature that allows you to modify your files seems to only be good in the case that you're bored.
I've heard that the Wi-Fi on the DSi isn't that great. Good if you just want quick makeshift surfing, though not if you want it as your own personal laptop.
The camera feature is fun if you have friends around and want to play around, but of course, the editing software on it is not going to be replacing art programs on the computer any time soon. Still, it would be fun to play around when you're bored.
Really, the little "upgrades" are just gimmicks to me. What I find better about the DSi is the hardware. It was improved of course.
But then there's the battery life, which was reduced.