The underlying sync software (Unison) has been around for years now and is regarded as stable. So syncing should work just fine, although you should keep a backup of your files just in case.
You can also use Dropbox and Encbox together if you're unsure: Point your Dropbox installation to ~/Encbox and have Dropbox sync your (then decrypted) files. So you can be sure to have backups, file sharing features, etc. and see if Encbox is stable enough for you.
You can also use Dropbox and Encbox together if you're unsure: Point your Dropbox installation to ~/Encbox and have Dropbox sync your (then decrypted) files. So you can be sure to have backups, file sharing features, etc. and see if Encbox is stable enough for you.