IIRC, the Samsung 7500 series has an input lag of 47ms and above. The 7100 is also about that high although I'm not quite sure.

The Samsung obviously looks better than the W804 though, but I personally feel that 47ms is a little bit too high for gaming. You may not be able to tell the lag if you aren't sensitive to it and aren't playing competitive games however.
So here's the deal, if you are going to get a Samsung ES7500, why not just get the Sony W904a instead? You get an input lag of 19ms, a TV that looks as good as the ES7500 (I personally feel W904 is even better with the deeper blacks and screen uniformity) and you pay less (last I checked).