I've got a Toshiba 43" LCD tv and had a similar sort of problem to you. After investigation it seems that in the shops, the tv's are set up for optimum conditions with harsh bright lights.
Of course at home, you don't have bright strip lights and as such you need to adjust the tv picture settings accordingly.
Try turning down the back light, the sharpness and the rest of the settings until you find the picture that suits your room lighting best.
It makes a big difference believe me, my tv was set to go back to the shop prior to the adjustments as I thought the picture was so poor. Now I think its fantastic, even on normal tv. Use a HD source and it looks out of this world.