I think it was worth a visit, but you only need a half day. If possible I wouldn't spend the night but head to Sibiu or Brasov and spend an extra night there.
This is a wonderful, little historic town. The citadel is wonderful to see and well-kept, making you feel like you have gone back in time for a while.
We went during the winter and there was hardly any tourist. It is similar to other places we visited in Romania, where the scenery is beautiful and the history is largely untouched, but the people are not overly friendly and sometimes makes you feel uncomfortable, like you are in someone's house you don't know.