You have a misconception if you think flat screens = better geometry. In fact it is incredibly difficult to achieve good geometry as the distance from the guns to the screen keep changing as the beam traverses the tube, and complicated adjustments are required to keep it a straight line. In a curved screen these effects are reduced by a more constant distance in all planes. I understand that geometry errors of up to 5mm are considered acceptable on setting up sets in the factory. My set has a straight bottom line, the top curves down to the centre then back up again and both sides are slightly curved, but all well within the 5mm. You only tend to notice if the picture is smaller than the tube face, I prefer to zoom out so that it is no longer seen. I did notice in some of the coverage of the recent terror attack that lines which should have been vertical on news programs were very curved inside the picture, but realised it was the lens used on the cameras to get the view width required. IE it could be errors in the recording rather than your tv that you notice as well.