Nice find, actually I would like something like this too! It has SiRF Star 3 which is extremely nice and is "weather resistant".
One thing I would research if I were you would be how long this thing lasts. It uses 2 AAA batteries so unless you buy rechargeable ones, wouldn't it be slightly troublesome? It would be nice if you found one with a replaceable Li-Ion which might make traveling and charging a little more convenient. I'm just suspicious how long these AAA batteries can power a GPS unit.
As an aside, if you are a Windows Mobile user going to Japan, you should have probably considered Super Mapple Digital (
http://www.mapple.net/smd/). It's probably one of the best GPS softwares for Japan and has a native WM client.