Metabones have been previewing their new Speed Booster EF adapter that has a lens element to scale the image form a full-frame lens down so it fits on the FS100 sensor. This means you can get a Full frame FOV on your super 35 E-mount camera.

You can read a review here: bnaro.com Archive Metabones Speed Booster – An Unbelievable Adapter (http://bnaro.com/b/metabones-speed-booster-an-unbelievable-adapter/)

A must-have adapter I would have thought?

Well it's not must have if you don't own any Canon full frame lenses. Looks cool though.

I've done a small review. More info at
New Metabones ‘Speed Booster’ adapter | Blog e-vdh.be Productions (http://blog.e-vdh.be/?p=320)

They'll have a Nikon version of the Speed Booster to use Nikkor lenses on the FS100 supposedly by the end of this month.