PushingPlay.com (linked above) has shared 7 things consumers should take note of while comparing the new DSi to the 'old' DS Lite. To quote:

Camera - While 2 cameras have been added, only one is visible while playing your games (the other is on the backside). This camera subscribes to the apple webcam mentality that you should ALWAYS have a lens pointed at you.

Finish - The DS Lite had a slightly shiny glossed finish, while the new one seems to be a bit more matte. Maybe this will mean less greasy fingerprints!

Power button - The DS Phat had the power button on the face. The Lite went with the power slider on the side of the system. It looks like the new DS is bringing it back to the old school and putting a power button on the face of the unit. It looks like it doesn’t stick out at all so it is probably pretty hard to hit accidentally.

Screen - Although it’s tough tell in pictures because the systems aren’t to scale, the new DS screen is .25 inches larger diagonally. The resolution remains the same.

Inputs - The new DSi has ditched the gameboy advance slot in favor of an SD card slot. Children with old games cry while hackers rejoice.

Online Store - The new DS will feature an online store ala iphone and PSP. This will be a great way for Nintendo to increase their revenue by having children ‘accidentally’ run up their parents credit cards buying them crazy poke-mans.

Size - The DSi has been working out and trimmed down 12% of its size. WiiFit Mobile confirmed?

Finally, according to Nintendo's U.S. Press Conference company president Reggie Fils-Aime stated that the DSi will not be arriving in the US until "well into" 2009. The primary reason for this being simply that the DS Lite is still in great demand, and Nintendo sees little reason to introduce a new piece of hardware this soon. More PlayStation 3 News...