Why would I want to import a DSi?
Aside from liking the foreign palette of colors, the only reason to import a DSi from Japan or elsewhere is for the country’s exclusive DSiWare. Right now the Japanese store is packed with silly Japanese-only games, some (probably many, by the looks of it) of which will never come in the US. The selection is already fairly good, and will surely only get better. Naturally, all of the games are in Japanese, though.