Thanks very much Anderson.
Yes I have, although not a professional calibration. I used a calibration blu-ray with loads of test patterns to get the brightness, contrast and colour levels as good as possible. It really highlights how bad TVs look on default settings. The colours are more muted now, which takes some getting used to, but then you realise how much more natural they look.
All my inputs go into my amp and from there to the TV so I only had to calibrate one HDMI. Definitely recommended to improve TV viewing and gaming.