I’ve had my DSi since it came out. I’m not exactly happy with it. It’s not a bad handheld by any means. It’s just sort of…pointless. The camera is worse than most phone cameras. The internet is slow when it works and after only a few pages it runs out of memory. Once this happens you can’t load any new pages. It was rumored that you would eventually need a camera to play ds games, but very few have come out with that as a requirement. The music player is decent at best. But, sadly, probably the best addition in terms of how it works. Also, if you play gba games, you’ll need an actual Gameboy Advance since the slot has been removed in the DSi.
If anything, I would either get a DS lite or wait and get the 3DS. The DSi was more of a stepping stone that became obsolete only a year or so after it was released. If you’re set on getting the DSi, then go ahead. But after the initial playing around with the features, you probably won’t use the camera, internet, or music player. I only use it to play DS games which is what you can do with any of the DS systems.