Like the original Olympus 15mm BCL, I feel this one as well is such a common focal length that no one is really gonna want to use it as an actual lens. Where as when Oly came out with the 9mm fisheye BCL, that was something I think people were interested and used because for most it offered something they likely didn't have in their bag already.
Perhaps this one and the Oly 15mm one could have been made more interesting to people by doing something like including a 3+ stop ND filter built in and market them as long exposure lenses. Those focal lengths lend themselves well to a water fall or a train station.
After all if you are going to come out with a gimmick lens, then gimmick the crap out of it!