We only know of two players which had a hardware brightness fault. If you have this fault it is equivalent to turning the brightness down to minimum - or worse - on a normal player. You can't see the display at all in daylight.
Other than that, the display brightness is very consistant on the Mk.2 and we've never seen a player exhibit abnormal display behaviour other than the two players I just mentioned. This would almost certainly be picked up during soak test, during which 32 players sit on a rack side by side - display variations would be very apparant.
I strongly suspect that the differences in viewing quality can be explained by screen colour, mounting position and individual perception.
If anyone is convinced otherwise then we'll pull your player in under warranty and put the issue to rest one way or the other. If it's normal, you pay for shipping.
Rob