Gimmick, plain and simple. The concept is not cost-effective to do right because it would take far too much engineering and delicate assembly to get an upside-down tonearm to track reliably with the even, low force required for proper playback. It appears they've got it to work, but too much can go wrong and I don't see it working long-term.
I also notice it has a NON-REPLACEABLE cartridge, and not a particularly good one in the Audio Technica AT95E. I stand by "gimmick."