Photographyblog tested the 14-28mm lens and concluded:
With a full retail price of £879.99 / €999.99 / $799.99, the Panasonic Lumix S 14-28mm F4-5.6 MACRO certainly offers a lot in terms of value for money, almost matching the capabilities and performance of the Lumix S PRO 16-35mm F4 at almost half the cost.
It may lack the PRO designation of its more expensive sibling, but for most users the new Lumix S 14-28mm F4-5.6 MACRO offers almost everything that you need from a modern ultra-wide-angle zoom lens.