Data SIM cards for overseas travel: good (b-mobile) and awful (Rebelfone)

I was in Japan and rented a MiFi hotspot for 10 days. Best $100 spent. Unlimited internet, usually about 4 mBit. Worked on the trains and I could make calls through my laptop.

The company delivered the hotspot to me at the Narita Airport Post Office with a self address envelope for me to drop it off when I was done.