The Tourism Agency has come up with a new transport offer for foreign tourists. It seems foolish to look a gift horse in the mouth but I can't help wondering if it works out as much of a deal. The Tokyo Transport Pass (PDF) will be sold to foreign visitors at Narita and Haneda airports only. You can buy a 2 day pass for 2,500 yen, or a 3 day pass for 3,000 yen. It allows you unlimited travel on the Tokyo Metro, Toei Subway and JR lines in the central metropolitan area. You can't use it on the journeys in from either airport or any of the private railways (Tokyu, Odakyu etc) except where they run on subway lines. Taking the case of the two day pass, you will need to travel on routes worth 1,300 yen a day for the pass to make any sense. I find it difficult to see how too many ordinary travellers would be doing that in the course of a typical itinerary.
If you look at page 2 of that PDF link above, you'll find some suggested courses. I think they are barking mad. They have you fitting in eight journeys a day, which may not look much on the page but is a different matter in the field. I might be wrong, but it also looks like your pass is valid when you buy it at the airport so you'll need to get some value out of it on the day you arrive. I don't know many people who fancy taking a lot of short train journeys after stepping off a plane in Japan. I don't think anyone doubts that the nationwide Japan Rail Pass is a good deal for tourists but the Tokyo Transport Pass looks far less useful.