I dunno about this sales gimmick comment, but it does seem to work for me irrespective of file format mode!
How well it works when compared to other methods of processing images is up to each individual user to determine.
(Ken Rockwell seems to think it's the bee's knees, last time I checked )
For me, I get hit and miss results(and hence why I rarely use it). There seemed to be no consistency and in effect you lose some control over the overall exposure in some situations.
I have used it, with some good results, will use it for specific conditions if the need arises.
As for sales gimmick, I don't think this comment is fair on Nikon, as it does work, as it's intended to do.
The comment on how it only affects jpg images is true if you don't use Nikon's software to view/process your NEF files. ADL works better on NEF files than it does on jpg files if the truth needs to be told.
You need CaptureNX to do this, but when you use it on an NEF file in camera, you can adjust the amount of ADL you've set on the raw file, or turn it on/off if you wish.
So if you set ADL to low, and in fact you wanted high, you make the change via CNX on the PC. From what I've seen(so far) it works exactly the same way as doing it in camera.
Conversely, if you turn ADL on and then you find that the image doesn't look as good as you initially thought, when you use CaptureNX, you can reset the ADL tone curve to off, and in 99.9% of instances the image reverts back to an exposure as if you hadn't turned ADL on at all. (there have been instances where the exposures have been slightly different when doing this reverting, but this is not very common).
If you use Adobe software(and many do) and you shoot NEF, setting ADL mode is a futile endeavour. You simply won't see any benefit.
On jpg images, once set, it's set! There is no option to undo, redo, or un-re-do.
There is some accuracy in the comment about just shooting in NEF mode and not to worry about it, but as I've seen, you are best off using Nikon's CaptureNX2 to do that.
In Capture NX2, there is a D-Lighting function for processing the NEF file on the PC, in the same manner as ADL does in camera. ADL in camera is a process which involves one less click to make the effect work on an image, but batch processing a series of images with D-Lighting is hardly an arduous task either!
ViewNX does allow you to alter the ADL setting on an NEF file, but not with the same degree of flexibility as CaptureNX does.