superdorkman, I live in Japan and usually Maemo mapper works quite well. Anyway I found something strange, I have a N800 with a bluetooth GPS and here to get a fix it takes 15 minutes or more where in my country, Spain it only takes 1-5 minutes.

If you intend to use extensively map routing buy a Japanese dedicated GPS the first day on your stay in Japan. Maemo mapper can do some routing but you have to download the route previously... and does not work very well because of the Japanese names... Don't know if there are many GPS with English maps in Japan, those I've seen are in Japanese, could be really difficult or impossible to buy one with Latin characters. Google Maps in Japan uses as well Japanese characters, somewhere there is a mashup that displays Latin characters instead of Japanese ones, but don't know if you will be able to use in Maemo Mapper.

Anyway, here at least in Tokyo there are many open networks so the Nokia IT is worth it for Internet use. Some friends here have the iPod Touch and while they can see 3 or 4 wireless networks, with the Nokia is easy to se 8, 9, 10... so more opportunities to catch an open network
If you finally decide to get the Nokia I recommend you to buy a USB charger and then in Japan buy extra battery packs, really cheap in here. I always carry a couple of them when traveling to avoid battery run outs...

Hope the information was useful, if not don't mind to ask anything!