My husband came to Bad Soden on business; I tagged along as a tourist. I found it very convenient to be so close to the train station (not to mention so close to an excellent little corner bakery...). We were there for five nights.
I can't really comment on the price as ours was negotiated through my husband's company, but it seems fairly reasonable. The included breakfast was phenomenal -- huge selection in a clean and spacious dining room, with plenty of polite attendants. The desk clerks were very polite and professional. I should note that only one of the four we encountered during our stay spoke English. This was not a problem for us as I had just enough German to get through the essentials. If you have special needs and don't speak German, I recommend using Google translate to e-mail them beforehand--they were very responsive to our e-mails before the trip.
Our double room was clean, comfortable and very large compared to what we've had in Europe before. TV got two English channels (BBC World News & CNN International). Bathroom was spacious and functional; plenty of linens provided.
My only complaint was that our room looked out toward the train station, and on Friday night it got a bit noisy, as that seems to be where the local teens hang out and there was some drama going on between a few of them. (Small town Friday nights are just as boring for kids as in the U.S., it seems.) Otherwise, a great stay.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC