If you are running a headless mac mini or similar, then it is not ideal to have to click 'connect' and 'ok' to mount shares. This is something that has been introduced in Sierra for some reason.
I had been successfully using some scripts described here: http://lime-technology.com/forum/index.php?topic=10274.msg , to monitor and mount my share containing my Plex media. This stopped working in Sierra, as it wont allow mounting to /Volumes as before.
After much searching yesterday I found that the author of the above scripts had put out a fix in the form of an app on the Mac App Store. Search for "AutoMounter". Supports SMB / AFP / NFS network shares. Seems to mount the shares into the users home directory rather than /Volumes to get around the limitation in Sierra.
I hope this helps some people and saves some frustration (or downgrading to El Capitan, which I was very close to doing!)