I've been using SyncThing for months and it's great. And it's open-source. They won't even release the protocol for btsync. That makes it suspicious. In today's world of government surveillance, back doors, and huge security issues on a nearly monthly basis, it's just not smart to use black-box software to sync your most sensitive information. Even if the btsync developers do have our best interests at heart (which they clearly don't if they won't release the protocol), they can still make mistakes nobody will catch, and it only makes it worse and more suspicious in a closed-source project.