The LG LN5700 LED TV has the same screen as the LN5400, but comes equipped with Smart TV features and motion interpolation. The viewing angle is great, but the contrast and black levels are sub-par.
The contrast on the LN5700 isn't good, which results in grayish blacks. This TV isn't the best option in this price range for a dark room (the Samsung F5500 performs a lot better).
The input lag is higher than the similar LN5400, but it shouldn't be noticed by the majority of gamers.