Yercaud is many times called a poor man's Ooty. I will probably not agree to that. It's less explored. Seriously, needs a tourism facelift. Ideally, if you are in Salem this is your perfect weekend spot I must say. Moreover, if you have driven in highways but not very comfortable with ghat roads, this is a good practice track. The 25 Kms. drive from Salem to Yercaud is a breeze of a drive. You will probably find the hairpin bends with the least amount of slope. 20 hairpin bends in all but you can mostly drive over them with a 2nd or 3rd gear with ease. Only once did I have to come down to the first gear to go over the hairpin bends.
If you are planning a trip with your car, a perfect travelogue can be found at: http://www.team-bhp.com/forum/travelogues/72561-bangalore-yercaud-hogenekkal-bangalore.html. I followed it verbatim and found it very useful. However, loop road may not be the greatest option to follow as you will be probably going through Yercaud country side several times depending on where you stay. This one is one of the sleepy townships you will see. The sightseeing places are not quite spectacular. The temples have been given a modern facelift and fairly recent. I do not see any reason why do not allow photographing them though. The lake is very small and looks fairly polluted not as bad as Ooty though. There is nothing to drive home about the dear park. The most attractive creatures I found were the guinea pigs. The aquarium had about 10-12 chambers. So not a great attraction as well. So is the park and the rose garden.
There are somethings I think, we definitely missed were the Kiliyur falls. Hardly, I knew when I reached the fall trail at 8:00am in the morning there was not a single soul on the trail. I felt it was probably too risky to try and got back.
I think the only reason you will like to Yercaud is if you have plenty of time for nature walks, relaxed 4-5 days of no activity and pure relaxation away from the day-to-day grind.
On the way back from Yercaud to Bangalore you will get to see Hogenakkal. The life in Hogenakkal is just the opposite. More than a fall it may feel like an open Hamam to you. But the mad rush to Hogenakkal is just the other extreme to be appreciated.