Summary: I've bought this filter to protect my lenses - 24-70/2,8 and 16-35/2,8. Slim frame is not visible even on the wide angle on 16-35, and filter is not spoiling picture. Only at night shooting with bright lights there can be some reflections, so it's better to remove filter in such conditions.
Excerpt: I use it to protect a tele zoom's front element without interfering with the optical properties of the lens. The original equipment lens cap fits on this filter, a plus. Hoya could use some decent filter cases, like the ones B&W offers with their filters. They are much handier and more durable in the field.