I look to see if there is a warranty. Nothing irks me more than having a T.V. go on the fritz in the middle of a crime show.
The quality of the picture is a selling point, but it's not a deal breaker. I'm happy with the regular picture we're all used to, but the writing of that crime show better be top-self.
I am also fond of checking what the warranty states. If you do not get this clear, things may not work out as initially planned. I love LED TVs and the picture quality has to be perfect. Does brand really matter?