The Nintendo Dsi was first announced on October 2, 2008 at the Nintendo seminar in Tokyo, Japan. It has since been released in Japan, and is slated for publish in "other markets" sometime in the first fiscal half of this year. Despite being a revamped version of the Nintendo Ds, there are categorically a lot of new features, unlike how the Ds Lite compared to the original, "dinosaur" Ds. First off, the Dsi is much thinner.
It is categorically 12% thinner than the Ds Lite, but that isn't the only thing changed, not even close. Nintendo also added two Vga cameras, one on the inside, which is pointed at the player, and one on the outside. Granted, these aren't real high ability cameras, but for a lot of the Ds's user base, which is under the age of 12, having a camera is categorically cool. The screen size has also been increased by 17% allowing for great resolution, and more room for those menus, which some game developers have a hard time scrunching into the screen. The Dsi also marks the return of the power button, like the customary Ds had, which is now settled on the lowest left of the lower half of the Ds, next to the touch screen. There are also 5 glow levels, now, compared to the Ds Lite's 4. The only question with this is that the battery life under the lowest possible glow setting has decreased by an average of 5 hours. At least the internal, rechargeable battery is still replaceable by the user.
Games
A huge addition to the Dsi is the Sd Card Slot. This allows you to take the photos off you Ds and put them basically anywhere, your computer, or even your Wii. You can also use your Sd Card to run downloaded software or listen to music on your Dsi. The only question with the addition of the Sd Card slot is the fact that they got rid of the Gba slot. This removes backwards compatibility, plus compatibility with games such as Guitar Hero, which required that slot for accessories. The second step Nintendo has made to seemingly compete with Sony's Psp is having upgradeable firmware.
Nintendo has also taken steps to make the Dsi much more house friendly by introducing parental controls based on a game's rating. There is also region locking inserted into the Dsi, which is only utilized by unavoidable software, so you'll be able to play games from any region.
Overall, there are a lot of good things about the Dsi, and a lot of bad things. It's up to you to rule either or not the Dsi will be right for you.
In Depth Nintendo Dsi report