Non-scientific, but I looked at the black bars on 2.4 material last night through a light tube (i.e., paper towel roll, lol) and as zoyd has stated, there were slowly rising and lowering black levels. It was not dramatic, and I cannot see these changes during normal viewing, even when looking for them.
Reminds me of CRT displays that do not hold black well based on APL. Furthermore, the scenes with lowest APL have the lowest blacks (where shadow detail is most important), so black detail is still there when it's most critical. (not to say black detail is not important in scenes with high APL, just more important in the darker ones)
While not optimal, this is much better than the jarring, distracting abrupt gamma change that was previously plaguing this display with minimal APL changes. Overall I am very happy with the improvement.