I've been struggling with this issue too. My 27" iMac's display has fairly bad backlight bleeding, especially on the left side of the screen, pretty similar to what's in your picture. It's really quite obvious when you're sitting right at my desk, about 2 feet away from the screen. The backlight bleeding falls off quite a bit if you stand further back (around 5 feet from the screen), but there's still an ugly blotch at the left-bottom edge, kinda like yours. What distance are people judging backlight bleeding issues from?
I've read various opinions about whether this is normal or not. Honestly it doesn't bother me in most day-to-day use. I don't really watch movies on my iMac, which would be the case that would bother me the most. So it really only shows up when I game, which isn't too frequent.
I've been having a hard time deciding if it's worth going through the replacement process. What was the replacement process like? Is it a big hassle? Do they send you a new unit or is it refurbished?
It does seem like some folks on here have panels without issues. I've played the replacement game and replacements never guarantee success. So there's a part of me that's not eager to get into that cycle... but then again..