[ChisaChi]

I went to Japan for 15 days and got a 7 day rail pass, which was definitely worth it for me. On the advice of people here I did the bulk of my traveling between cities in the 7 days I had the rail pass, and spent the rest of the time in Osaka and Tokyo where it isn't so useful.

Basically the bullet trains are quite expensive, so if you're planning to travel quite a distance multiple times in your holiday then it's definitely worth it. Using the rail pass I went from Osaka to Himeji, Hiroshima, Miyajima, Nara, Koka, Kyoto then up to Tokyo, then up further to Karuizawa. If you're just staying in Tokyo, for example, and not planning on traveling outside very far then it probably isn't worth it.