I've been using the Tamron 70-200 2.8 on our FS-100 and FS-700 with the Metabones Smart Adapter and it's been nothing short of amazing! The image quality is superb and it produces great bokeh. The downfall of the lens is its on the heavy side. As a photo lens is has poor autofocus capabilities. Can't go wrong with it as a great, long video lens.
On 02-24-2013 11:55 AM, you said the FS100 and FS700 cameras are using the Metabones Smart Adapter, and it allows both cameras to control the iris. I assume you mean the camera controls the iris electronically?
You also listed the Tamron 24-70mm f/2.8 and the Tamron 70-200mm f/2.8 as the lenses you use with this adapter. Are these lenses using Nikon mounts?
I have the Nikon mount version of that lens, I use it on my FS100 with the Novoflex adapter.
It's a nice lens, I like it. Biggest problem is short focus throw, but I can overlook that as it's the only gripe I have with it.