FWIW, if I put up a 100% white solid, our Panny 10UK 37″ definitely looks grey compared to Cinema Display, but fairly close to my Sony CRT.
I think it’s the nature of LCD technology to have very bright whites. It’s not that your Panny is grey, but with a bright LCD to reference it against, it looks dimmer.
The panny looks gorgeous with regular footage – but pure white isn’t it’s strength.