I was worried about pixelation on the HD Ready Plasma especially since the size is 50". Normal viewing distance is 12-13 feet but sometime it can be 5-7 feet when sitting at the edge of the bed or roaming around the room during TV usage.
Please read the thread with title "HD ready vs Full HD"..
That has all the info you need.
For 50", it does not make a difference for normal viewing distances.
I have personally seen the 50"-ers in action and particularly for the B450 that you are after, there is'nt a difference between the 42" and 50"-ers..
The pixellations (if the transmission quality is really bad) can be seen from 6' for 42" and 7' for 50" but at those distances it will not be possible to see the TV for any meaningful amount of time. (I agree you tend to have a glance while moving around the room but that is acceptable).
And the off-angle viewing of plasmas is god given.. Currently Iam sitting 5 foot almost 90 degrees from the centre of the TV with a laptop with frequent glances to the TV.. No change in picture quality!! I only wish LCDs are this good..
The best guy is the netfreak who has brought home the TV recently.. Ask him for the experience..
Edit: My 42" already is beginning to look small..
Don't settle for anything less than 50"!