I had been to Yercaud on a public holiday and the place was terribly crowded. But Yercaud is definitely a place worth of 2 day visit (apart from weekends and public holidays).
I enjoyed the boad ride on the misty lake in Yercaud and the hike to the waterfalls. There are some beautiful view points built by the forest department.
More than the place itself; the 32-Km loop road drive to reach Yercaud is a worth to explore.