As I mentioned in the previous thread on this, each of the four main boards are 13 feet by 16.8 feet, which if I calculated correctly is equivalent to a 250-inch screen.
UPDATE: Mgoblue.com has a video up showing the scoreboard being raised. It looks perfectly straight in the video, so the crookiness in the picture noted in the comments is probably from the angle from which the picture was taken. The video features an interview with Craig Wotta, the manager of Yost. He says some lights and banners are being moved to fit around the new scoreboard.
UPDATE #2: The mgoblue.com video has been posted on youtube. I can't get it to embed here but have placed it in a comment below.