I've been using this lately to sync folders across multiple machines. It's working really well, I've only run into two issues so far, one is that with a Windows machine (the rest are Macs) and Office files, you get some sort of locking error (but it still seems to sync), and a more obscure one which is that with Vagrant VMs there's some issue with file ownership (that second one is probably a bad idea anyway).
I've been on the free one but right now they are half off as well for the "Pro" plan so will get that shortly.
https://www.resilio.com/individuals/