If you've been wanting a DSi, it does come with some nice features. You have the cameras, the DSi store, a better web browser than any homebrew version for the DS, and a nicer interface to boot.
You do lose a slot 2 though which is disappointing for those with no other way to play their GBA games (I mean legit, not ROM's).
The DSi should be more inexpensive at this point, especially if you find a good used one. Depending on the reception of the 3DS in your area, you may be able to find one for relatively cheap if you go to the right place.