Hi, Harvey. My boyfriend and I did a 10 day WWOOF experience two years ago and had a fabulous time. We really liked the family, the work was hard but not unbearable, and it was very educational. I think that probably you have to be careful about the host that you choose, and that contacting them in advance could help you figure out what you are getting into. I would also take seriously the information about the host's language preferences; I speak some Japanese, but one of the other WWOOF'ers who arrived after us didn't, and I'm not sure what kind of experience he would have had without us around.
Anyway, I would definitely recommend it; we are still in contact with the family we stayed with/worked for!
Best,
Jean