We just travelled to Japan for 10 days and hired 3 1gb data cards for our iphone 4s's. We got two from bmobile and one from econnect. All worked fine for both but I just wanted to say that even though econnect was slightly dearer 4600yen vs 3800 yen (or something like that) their communications were much better than bmobile. Econnect emails were answered promptly by people that speak good english, and I needed help with the settings whilst there (cos I couldn't find my way round the iphone!!) and they replied straight away.
Also econnect were able to deliver a sim card to our hotel within 24 hours notice when I contacted them by email.
BTW we used the skype messaging service to contact each other whilst out and about. We couldn't seem to get the skype voicecalls up and running. Have to work on that now that we are back home. Also you can't hotspot with the cards.