I got the Sigma USB dock the other day, not because I thought my 35mm needed any adjustment but because, well, for £40, why not? In any case, I can see myself using more Sigma lenses if future releases match up to the 35mm.
Just some feedback for now. I connected my 35mm to the dock and was mildly surprised to find there is already a firmware update for it. I haven't yet spotted any performance improvement but psychologically, I somehow feel that my world is a slightly better place for having the latest firmware.
The only adjustable parameter on the 35mm is focus calibration, a la AFMA, rather than the custom settings available on the 120-300mm such as focus speed, minimum focus distance, etc.
One thing that I find slightly bothersome is that I have yet another cable to connect to my laptop: three types of device - camera, tablet and now the Sigma dock - all with different plugs. I've no idea why there are so many different standards for these small plugs.