Stayed one night at this B&B directly across the street from the tourist information center. We had talked to the information center about rates and she said they ranged from 35-90 euro, then we walked across the street to enquire having read about it in lonely planet.
It is run by a very elderly lady, but nice as can be. She charged us 40euro for the night, no breakfast. Also, the rooms were not en suite, but the bathrooms were very large, private, and never waited in line. We got a room on the top floor that was large, and clean. The bed was comfortable and it was very quiet.
The B&B is perfectly located right around the corner from the castle and across from downtown. Across the bridge was a pub called Matt the Miller's, excellent food and on Monday nights have a live cover band.
We weren't expecting much from Kilkenny, but it ended up being one of our funnest nights in Ireland.

And our elderly host waited up for us to make sure we got home. Such a... more