Value for money: 4/5
Ease of use: 5/5
The rail passes are fantastic, unlimited travel on JR trains made life in Japan very easy.
Often people will caution you that unless you plan on extensive travel within Japan, they are not good value for money. This is possibly true if you only see one or two cities, but we visited 6 cities on a 14 day pass and some of our trips would have been very expensive if we'd had to buy the tickets individually. Train travel in Japan is so efficient and easy to use that you can easily take a day trip to a city hundreds of miles away and return in the evening without issue.
With the rail pass, you can easily board any train, including the unreserved bullet train carriages, without any prior booking. This means that travelling on impulse or changing plans is very easy. If you wish to have a reserved seat, which we would recommend for long journeys, you simply go to the booking counter and they will give you a pass. We found the Hyperdia website useful, using it to write down train numbers, times and dates which the non-english speaking staff could easily understand. You can also book your seats way in advance at any JR booking counter, allowing you to plan your entire trip if you are organised enough.
We had a green pass which allows travel in the equivalent of 'business class' but the regular seats are still pretty good and the additional expense was probably not worth it. One of the advantages of the green cars is that they are less popular so you are more likely to get a booking for a popular route.
The pass does not include the Nozomi trains, but they are identical to the regular bullet trains, but stop less. On a big trip from the north to the south, the Nozomi does save some time, but not enough to warrant their additional cost. The pass covers JR buses as well as JR Ferries, helpful if you want to visit island attractions such as Miyajima.