Since the mount contains no optical elements, there's no degradation in image quality, and you'll also get the ability to focus to infinity with many lenses. But, there are a relatively sizable number of other caveats. As you might guess, the lenses have to be used entirely manually—there's no AF or electronic aperture control. Nikon lenses have to be used with a mounting shim to adjust the distance slightly to use them accurately; OM mount lenses need to be fixed at maximum aperture to work properly; Konica lenses can't focus to infinity; and C/Y lenses need a slight modification removing part of the aperture lever to fit properly. Also, it won't work with weather sealed Pentax cameras, though there is a variant for that in the works.