Yes, mine too. The brightness at max doesn't match max on the 3, and over the whole screen there is like a dullness or haze.
That said, comparing the two: the 3's tint isn't as even as the 4's
Looking at photos on both screens, while subtle, the iPad 3 wins every time. The detail stands out a bit more, it looks a bit smudged on the 4
Diagonally on a black screen, the 3 has a pink cast, the 4 purple.
At about 120°-170° looking up the screen, the 3 is still clear, the 4 hazed over.
The yellower screen on the 4 is softer on the eyes.
The 3 has more contrast than the 4 does, text stands out more.
However my 3 has some dust under the screen (near the button) and a slightly brighter patch (right vertical side, bout 1/5 way up) which can be noticeable when reading places like here.
With all of that I am not sure which screen I'd actually prefer to have at the moment. I do notice improvements in the 4 but the screen puts me off a bit, so strongly debating the staying with the 3 (with its flaws but better contrast/clarity), keeping the 4 (with the haze) or getting another 4 to compare it against the other 4.