basically I feel viewing distance is subjective...especially after I get my 42" LCD TV.
I feel that a minimum distance of 2 metres from the TV for viewing comfort. Any closer will make me awkward. First of all, what kinda of experience are u looking for... a movie theater experience, then my frens...a 46" at 2m oso not enough. maybe u need 100"...
However, I not only use it to watch my movies but also news and daily programs. 42" at 2m is more than enough. I feel it is big enough and for SD programs not so pixelated. The bigger screen u get the more pixelated it will be.
Another issue is the brightness, is also up to individuals. I find it too bright if I switch to dynamic mode...yes the colour is nice but I feel it is too straining for the eyes if you are at 2m away from the TV lor.
Ideally I will say the viewing be around at least 2-3m and a reasonable size will be 42" onwards.
More importantly....don't sit too near to the TV. It's bad for the eyes.