If you walk up close to a 42" TV, it's going to be blurry at 3 feet....and this is a tru HD 1080p TV......blurryness will be less noticeable at 6 feet or so and disappear completely at about 10 feet.
The human eye looking at a screen will start to notice individual pixels at normal sitting distances at about 96 pixels per inch. With a 24" screen at 1920 x 1200, the ppi is 94. However at 42" at same resolution , you're down to 52 ppi which is very grainy.
As you can see here:http://reviews.cnet.com/4520-7608_7-1016109-2.html
the minim viewing distance for a 42" TV is 5.3 feet.