It's entirely P2P, so no 3rd party hosting of your files, no trusting someone's crypto/update schemes, or having to set up your own servers (although you still can easily add it to a VPS if you want offsite). There's also a nice mobile app:
You can also securely share directories with another person who uses Syncthing, I've found autosync directories are easier than using something like Airdrop for sharing photos with family.
Has a 5GB free tier, higher tiers cheaper than dropbox.
Based in Canada if that matters.
Or Syncthing as others have pointed out.
I'm still thinking which is best. They're slightly different use cases. But generally, I'd only really trust it if there's open source, otherwise there's lock-in.