I got a refurbished camera and lens from Nikon. I did have an issue with the camera at first. I was getting spots on my pictures from the mirror slapping lubricant on the sensor. It finally cleared up after usage and cleaning. No problems with the lens.
I bought a factory refurb D5100 and it was perfect and hasn't missed a beat. Just be sure you get a factory refurb from a dealer and not an owner refurb.