I was in Cuenca this past June, and personally found it very nice, but not really special. I went by AVE train from Valencia, spent one night at the Parador across a pedestrian bridge from the old town, and the next day picked up a rental car in the new town, and went off in different directions. The AVE train station is very modern and nice but a few miles from town. When I arrived, after a pit stop in the station, there were no taxis there, and only one person around. Fortunately he had a cell and helped me call a taxi. The problem with a day trip is often that you have to add up the transit time and the costs of transit for your group, and then decide if the benefit of the visit outweighs the costs, compared to what you might do right where you are based.