I think the basic problem with the Horizon is not image quality, it's quality control. There are stories out there in cyberspace about people having to return 2 or 3 Horizons before they got one that worked. The main complaint appears to be cogging: the lens does not move smoothly across, it moves in little jumps that leave banding problems on the image.
This is what I have gathered from reading.
“There is hardly anything in the world that some man cannot make a little worse and sell a little cheaper, and the people who consider price only are this man's lawful prey.”