BitTorrent Inc. also updated their desktop app Sync today. The app is now out of alpha stage as we got the first beta build today.
It now features a basic versioning feature called SyncArchive. It would create versions of the files in a special folder making them easily accessible.
One-time Secrets (shhh)
Option to exclude specific files/directories
Advanced preferences configuration
Support for additional types of NAS devices
Improved Linux WebUI
Bug fixes and other improvements