I had a NHT surround system set up like that, and it sounded very good. Sound dispersion worked well too, with very little localization of the speakers. Friends couldn't believe that my modest NHT system sounded as good as it did, in that room.
The television was centered to the corner, with the center speaker just below it, and the left/right mains further out, just flanking the TV. Plus, that allowed the surrounds to be placed along the diagonal of the room, in the opposing corners. I got really nice surround separation from that placement.
Now, that said, I only think the reason that I used that placement configuration, was the fact that this particular room was square. For a square room, it works well, to help break up room modes, since the speakers aren't symmetrically placed to parallel walls. For a rectangular room, I'd still probably use a standard rule-of-thirds, or short-wall/long-wall placement.