I use my iPad for navigation all the time, I love it. Since I use it in a different rental car each week, I just prop it up between the transmission selector and the stereo/AC/heater panel. I tried a few different mounts, but I couldn't find anything that was small enough to carry on the plane each trip. Plus, with no mount, it makes it much easier to quickly slide the iPad under the seat, or in my purse when parking the car. Additionally, there's no mount to attract someone who may try to break in to find a possible device.

I use the Navigon app (from Garmin,) for North America and it works great. But, while several other countries/regions are available, unfortunately, there's nothing for Japan yet.

From the Garmin blog, "The NAVIGON app will roll out in the U.S. first and later become available in Europe, Australia, Japan and China." http://garmin.blogs.com/my_weblog/20...l#.Ur2vEdJDtAo

Europe, Austrailia, New Zealand, Russia, Brazil, India, Turkey, Mexico and Middle East are already available from Navigon, so hopefully soon for Japan and China.

But it does looks like there are several offline apps for navigating in Japan available now. Just nothing I have had any experience with.