Hi all,
is there any robust solution yet to sharing/syncing tags across
machines.  (e.g. a desktop and a laptop).

I see a couple of solutions:

http://www.muchsync.org/  -- but is this still being developed?

https://www.reddit.com/r/linux/comments/2kcznk/notmuch_syncing_tags/

Which do you recommend?

Thanks, Stephen