Stayed one night in C-loop in the Fall and it was excellent!!  Weather was great, the lack of people was perfect, and the facilities were more than comfortable.  Sites ranging from level with asphalt and sidewalks to the fire pit to near-natural for that full tent camping experience.  Plenty of full hook-ups interspersed with electric only and no services.  Something for everyone.  

The state park has numerous hiking and biking opportunities and probably some fishing as well.  The lake and pool facilities were closed but the scenery was still in full effect.