cokin magnefix

Hi, Cokin has released a system of additional lenses (teleconverter

2X and wide-angle converter 0.5X)to be fixed with amagnet to the

front of the lens. To do that is provided a small adesive ring that

has to be attached permanently to the lens. Has anyone there used

this system? Do you think it can provide acceptable quality? Is

there any danger to damage the lens or the small motors for AF and

zoom lens with the weight of the additional lens?

best regards