I too have had positive experiences with Global Advanced Communications on six or seven occasions.

In the past I have rented a japanese phone and also gave up on trying to find pre-paid SIMS from the local carriers with voice and data. While I initially did it reluctantly renting a MIFI device which I carry in my jacket pocket or briefcase has become my preferred solution. I realized I don't place many local calls but I do use google maps, email and the web heavily. So unlimited data is much more important to me.

Additionally, at least in Tokyo the MIFI data rate is frequently faster than the hotel WIFI data rates. International voice calls via Skype over the MIFI connection work well and you do not have to be too sensitive as to your location. There is even good reception on most subway platforms.

They do rent additional batteries for the MIFI device. These are external and not replacements for the internal battery. I would have preferred the later. On subsequent trips I used my own external battery which has higher capacity and could recharge an iPhone, iPad as well as the MIFI device several times.

The only hiccup I ever had was that at Haneda when taking an early morning BA flight the shop with the Post office on the departures floor was closed. It took a little investigating to find a Lawson's (convenience store) on another floor which was open for dropping off the envelope. Other than that one instance their whole process of receiving at hotel and dropping in a Mailbox before departure works smoothly.

I've never used the pickup option at the airport because I haven't wanted to spend the time at the airport upon arrival.