If you have a day to spare I would really recommend the Hakone loop. A Hakone free pass gets you access to all the ropeways (cablecars), buses, trains and even the pirate ship involved in completing the loop and on a clear day the views of Mount Fuji are awesome.
Yumoto is a good base for the loop and the Fujiya hotel is right next to the station. It is very very comfortable; huge room, 2 big beds, sofa, etc...Breakfast buffet was excellent, a extensive mix of japanese and western breakfasty things and you can go down to eat in your yucata (nice dressing gown provided in your room). The onsen is great; I'd never tried one before and this hotel makes it very easy even for a nervous first timer!
On the downside there are only a handful of restaurants in Yumoto; these do close early and on a Thursday evening we found most were closed even at 6pm. Also the hotel is seriously-not-cheap. I think this is because of the area; if you are going to visit Hakone it is probably best to plan in advance and hunt around on Agoda for a good deal as everything seems pricey.
So Fujiya is certainly recommended if you want a nice hotel and easy onsen experience, but are not working to a tight budget.
