Located in Akita Prefecture and no train station really close by, Nyuto Onsen is not the obvious choice for the tourist in Japan. However, if you developed a taste for onsen and want more, Nyuto Onsen is the place for you. See my trip report for details.
If you have the chance, I would certainly recommend that you visit an onsen in Japan, and these old onsen are the best. Judging from the questions I see at the Japan Guide, most first time visitors worry about the nudity. Fact is that most onsen baths are separated by gender and everybody is too busy enjoying the soak to worry about the others.