The thing I find with auditioning TV's in the electrical retailers is the setup is far from ideal. The TV is taken out of the box, plugged in and turned on. I doubt that any of the settings are changed, all the picture enhancement processors are probably on by default which can improve or harm the picture. The source that is fed to the TV is usually shared between a number of TVs thus degrading quality.
I have seen an LCD setup correctly with the colours, sharpness, contrast all perfect and I was very impressed. Ok so not as good as CRT but very, very close. The thing that LCD has going for it is the geometry which is a big bug bear of mine with regards CRT.
The blocking effect you are seeing could be to do with the image processor settings on the TV, 100 hertz CRTs have this as well. The one thing that LCDs do suffer from is 'rubber face' syndrome which is impossible to get rid of.
Wealth of discussion on this over on avforums.