I can post the same stuff here I posted in another thread:
Remember to be very careful if you consider a TV as your monitor. Make sure that your tv has a decent input lag rating. Many LG tv:s have 100+ millisecond input lags where some new Sony models are as low as 20 milliseconds. The best monitors can get up to 1.5-4 milliseconds.
Input lag is very nasty for fast games. You can't see it while you play but if you would put a fast monitor alongside of your lagging screen you would see how your screen lags visibly behind the other screen. While your aim is spot on on the fast screen, your slower screen is still not showing your aim is spot on but somewhere else - and if the enemy moves and you have to correct, you're again mercilessly behind the curve. Basically what it means is that fast moving targets are nearly impossible to hit using a lag screen.
You're going to feel like you suck at fps if you have a lagging screen and the players with fast screens pop headshots after another as aiming is that much easier for them.