It is not a gimmick. The Burris ballistic reticles work and this automatic elevation and windage compensation works. Bushnell and Zeiss also make one. The military uses them.
I have shot one a variety of odd ranges, out to 600, mounted on a Remington 700 in 7.62 NATO, and it worked like a charm. The glass is good. I have looked through the Bushnell and the Zeiss, but not fired through one. The Zeiss had a bit better glass, as one would expect.
Search the threads here, as I posted about this, and several SDUK members had owned or tried them.