HDTV Input Lag
HDTV test mentions that the Samsung has a major amount of input lag. Due to the lack of reviews on the 55x4500/xbr8 I called Sony's help-desk and they told me I would not have any trouble with that on the Sony. I couldn't find any complaints on the internet about 55x4500s having input lag either so therefore I recently ordered one (It hasn't arrived yet).
I think it is a bit disappointing you did not review this aspect because for me, and many other people with a game console, it is a deal-breaker and worth the extra money. Bear in mind that too much input lag makes online gaming pointless and therefore it eliminates half of the fun of having a 'next gen' game console.