I'm the OP of this post:
http://www.dcurbanmom.com/jforum/posts/list/645036.page#10972324
My grandmother lives in Pittsburgh so we do the drive 1-2x a year. I'll say the best stop we ever did was over this winter break, when we left her house a little before 8am, then skiied from 10am-3pm at Seven Springs - then drove home. We plan to do that again next winter!
One year we got forced off the road due to a snow storm, and we stayed over night at Omni Bedford and enjoyed it.
Otherwise we usually stop for food in Cumberland, MD or Breezewood, and never get anything good!