PhotonsToPhotos measured the S5 sensor dynamic range. As you see it performes slightly better than the S1.
Photographyblog tested the new Lumix 85mm f/1.8 S lens and concluded:
With a full retail price of £549.99 / €679.99 / $599.99, the Panasonic Lumix S 85mm F1.8 is something of a no-brainer in the value for money department. It makes for a very nice partner when paired with the diminutive Lumix S5 camera that we reviewed it with.
Overall, it certainly fits the bill as a fast, high quality yet affordable portrait prime lens for Panasonic S full-frame camera users.