Source

Should make the game look better. Comparison video (Of older version of the mod), the difference is ridiculous.

EDIT: This post shows the depth of field in the latest version of the mod.

EDIT2:

Official Response

The dev team is completely dedicated to getting the most out of each platform, so the notion that we would actively downgrade quality is contrary to everything we’ve set out to achieve. We test and optimize our games for each platform on which they’re released, striving for the best possible quality. The PC version does indeed contain some old, unused render settings that were deactivated for a variety of reasons, including possible impacts on visual fidelity, stability, performance and overall gameplay quality. Modders are usually creative and passionate players, and while we appreciate their enthusiasm, the mod in question (which uses those old settings) subjectively enhances the game’s visual fidelity in certain situations but also can have various negative impacts. Those could range from performance issues, to difficulty in reading the environment in order to appreciate the gameplay, to potentially making the game less enjoyable or even unstable.

Thanks for playing Watch Dogs and stay safe on the mean streets of Chicago.

-The Watch Dogs Team

Thanks Mew2 for linking the response