At NRT right now and dropped off my "PocketWifi" from Global Advanced Communications at the post office.
Had it for just under two weeks traveling in and around Tokyo. Highly recommended.
Pickup was as expected, waiting for me at the NRT post office. They also had provided me with tracking information and email alerts. It actually was at the post office two days prior to my arrival.
Came with a small case, AC charger, small USB cable, and the unit itself.
It also came with prepaid return envelope, all labeled and ready to go. I simply popped everything in it, and dropped it back off at the airport. Really easy.
Overall, I would definitely do the same thing again.