Ideas to reduce backlash
Many (if not all) of those ideas indeed remove zero-force backlash, but introduce an elasticity to the gear mechanism, creating an offset that now depends not only on direction, but also on load. That way, when e.g. the x-axis printhead accelerates, the gear will compress, then decompress when it reaches full speed, compress in the other direction when braking and decompressing again when stopped.
This is pretty much the same characteristics that people with mechanically weak printers, e.g. the printrbot, see. The only application where these methods are valid are those that only require a precise position at stand-still with no external forces.