Unfortunately, Syncthing only supports a subset of what Bittorrent Sync does:
- There is no tracker/relay server infrastructure. As a result, Syncthing doesn't work if two peers are behind a firewall/NAT without uPnP or manual port forwarding. The number of peers behind carrier-grade NAT is only growing (IPv6 migrations) and if you are often on the move (hotels, etc.) you have no control over the firewall.
- Syncthing does not support selective sync yet, let alone with the ease of BTSync where it is a Finder/Explorer extension.
- Syncthing does not support link-based sharing, which is handy if you quickly want to share something with family/colleagues.
- Syncthing is too hard to set up for most family/colleagues.
tl;dr Syncthing is great for synchronizing two machines on networks under your own control, but it is not a nearly-complete P2P replacement of Dropbox like Bittorrent Sync is.
