DoCoMo is also now advertising their national Wifi access network for travelers - 900円/week. This seems comparable to many Western ISPs providing public wifi from their customers' modems. They claim good speed but the real acid test is of course how common and widespread they are. Do they have coverage in JR stations, or trains? What about walking down the street in Shinjuku, Shibuya or Denden Town?

http://visitor.docomowifi.com/en/details/[/QUOTE]

I signed up for the service in August for our trip to Japan. It was more or less worthless. My iphone would hold not a connection (did not try my laptop) and I had to re-sign in each time to the service. You have to sign in to access the wifi and then sign in on a login webpage using a different set of credentials. After about 10 minutes of trying to get it to work in Kyoto, I decided to just get a data sim.
As far as availability, I did notice that my phone would try and connect to their service at number of train stations and department stores (more common in Tokyo, it seemed).
The service seemed sporadic and I quickly stopped trying to troubleshoot the problem. I did make another attempt in Tokyo but gave up after a few minutes