I can only say RB displays just fine on 32" here with HDMI. Haven't tried BiaB on it. All of windows 7 has worked well here so far. The one I use most is also 720p, but I have used 1080p and did not notice difference.
As you mentioned, it does work very well for video and online TV.
Can't comment on Word, but Powerpoint worked well also a couple times

I don't own anything Sony.
Just noticed; you said 50". That may be a big part of it. I have a 42 that doesn't look bad, but not as nice as the 32. Maybe 50 is worse yet with the screen resolution you are using.