I have an NTSC-J Wii. It's neat. I can see the weather and news for Japan. A few weeks ago we got some special Mii's sent to us that were featured in a popular TV commercial for a while there. But having all the VC games in japanese can be a buzzkill, especially for RPG's. Doesn't matter for most games though.
I say go for it. I've seen what the PAL market has gone through in the past and if I lived there, first thing I'd do whenever a new console launched in japan is import one. Why wait two years for a game the rest of the world is already playing??