So after about 10 months I noticed this cool ghosting issue on the my MBP  – after some research it seems to be pretty common on LG displays.
http://www.macrumors.com/2013/03/15/apple-faces-class-action-lawsuit-over-screen-ghosting-on-retina-macbook-pros/
in the terminal – ioreg -lw0 | grep \”EDID\” | sed “/[^<]*</s///” | xxd -p -r | strings -6
suggests I have an LG screen.
 

 
I have an appointment at the Apple store tomorrow.