"The result of the investigation into the lower peak brightness found on the 55Q7 sample by Rtings.com is; Damage to the sample in shipping resulted in a lowered peak brightness. The damage effected the performance of the light guide plate, and this lowered peak brightness by 33%. (the sample picked by Rtings offers 782 nits, when measured based on 10% window peak luminance. An actual figure according to measurement by Samsung is 1160 nits.) Due to the defect caused by the damage, the product fails to meet the specification standard and its peak brightness was compromised."
It is hard to know how widespread the issue is, but our 2 units that we bought, shipped weeks apart, were affected by this. Therefore, you should expect a variance of brightness on the Q7F depending on how smooth the shipping/distribution went with your unit. This variance of brightness may not be noticeable to the average consumer however, unless you put them side by side.
Also worth noting that even with the numbers of expected brightness that Samsung provided, it wouldn't affect significantly our overall scores (you can check our scoring formula by clicking next to one of our ratings/tests, or you can also check our review of the Samsung Q9F which is similar but brighter), so it doesn't affect our recommendations since with the current price, it isn't competitive and falls short of other TVs.
Update 07/05/2017: We improved the TV's brightness by realigning the light guide plates by dropping the TV, as shown in this video. The brightness increased a bit, by 30-100 cd/m², at the cost of worse uniformity. The brightness scores have been updated, and an updated brightness plot is shown here: