Going on to Japan for a short vacation & I'd like to be able to use my N900 there. Anyone know if the N900 can be used there? All I really need is data.

The only option that looks viable is this http://www.bmobile.ne.jp/english/3g.html which is a USB 3g modem precharged with 150 hours of usage time. I'm assuming it contains a sim that can be used in the N900? If this works can this be resold too since 150 hours is way more then I plan to use & with the device costing $400.

If that doesn't work is there a rental phone with reasonable data rates that could possibly be tethered to the N900?

Well, according to several sources, including hear-say and http://www.japan-guide.com/e/e2223.html, Japan doesn't use GSM at all. So, presumably, no SIM card either. On the other hand it looks like that device in your link may not need one. BUT, it'll need host mode.. which the N900 doesn't support. Your laptop would, though.

Wi-fi should work. Japan uses channels 1-14 while your N900 may be set up to use only 1-11 or 1-13, depending on your location. But as long as the network you try to access isn't on channel 14 you should be ok. I don't know anything about the status of open-access networks in Japan however.

I just came back from Japan a month ago and I had my N900 with me. Most mobile phone providers don't use sim cards but it doesn't really matter since as a foreigner you can't get a contract anyway and there are no prepaid phones except some hilariously expensive ones that you can get at the airport or in selected mobile phone shops (This page has good information also concerning rental: http://euc.jp/misc/cellphones.en.html).
The N900 works perfectly fine on the 3G networks but since I suppose you don't want to do data roaming this is only good for calling.
It was however quiet easy for me in a lot of locations (might've been lucky) to find free/open wifi connections and I never had any trouble connecting. This was good enough for me. Sorry I don't have better advice on how to be online whenever you want with your N900 (except data roaming of course).

Well I just researching more on this & I guess this was what prompt me to ask about the b-mobile device. Poster here claims it uses a sim that be used in a phone.

http://forum.gaijinpot.com/showthread.php?t=79804

Other then this the other option would be the same USB modem, but with a Cradlepoint PHS300 personal wifi device. This isn't ideal though because of the low 90 minute life.

I wonder how much 150 hours is converted to $/data?

i was in japan again last month. i borrowed a vodaphone/softbank SIM from a friend and it worked perfectly in the n900 in 3g mode (no GSM available).

wireless worked fine when there was wireless available, which was almost never.

here is the old thread we were using for this topic:
http://talk.maemo.org/showthread.php?t=31680
there is a bit more info in there if you manage to wade through all seven pages

Already looked through that thread, but there was no response on if things worked out there.

Know about Softbank, but data rates are .32 yen/ 128bytes for a rental. I suppose it's much better for a resident/citizen with a contract.

yeah it is absolutely ridiculous what they charge if you arent a resident.

if you can do without internet while roaming about, you might want to see if one of those small wireless routers would cost less than a softbank rental and subsequent data fees. at the very least you can plug in at a hotel or a friend's apt and get internet then.
far from ideal, but unless you can borrow a SIM on contract, youre going to have to pay too much for 3G data. -_-;