Yeah, my mid 2011 27inch went exactly the same a couple of months ago. The screen started to flicker for a couple of weeks and then got worse until the whole left half of the screen was virtually black.
Took it to the apple store and they immediately confirmed the LCD panel had gone and replaced it under warranty £420.00 I think it was so lucky I didn't have to pay for it but think its pretty poor to get such big failures so quickly after purchase but maybe I was just unlucky but plenty of similar stories online so not exactly a rare fault.