Load a black background as a photo to view full screen. Get in a dark room. If you see any light bleeding along the edges, then you have the issue. However, I had this on my first iPad 2 and didn't worry about it at all because I could not even see it if anything is lit up on the screen. Typically, that is way brighter than the backlight bleed.
I checked my iPad3, I don't have any issues. It is more uniform than my first iPad2 was. However, this works on a case-by-case basis, so you have to check yours. But even if you do have some backlight bleed, don't freak out. It may or may not be a problem. You should consider if it hinders you in anyway. If the backlight bleed means that you can't enjoy watching movies on your iPad because of this extra light, then return it to apple for a replacement. But if you can't even notice it on the darker scences in movies (when it is more likely to be noticable), then don't worry yourself.