I've had a few problems with temporary Vim files that are long gone but which Syncthing refuses to forget about, but other than that it's been smooth.
My experience with Syncthing on a Raspberry Pi has been that corruptions happen very often if you write to the SD card a lot. I have set my Raspberry Pi in a way that the Syncthing config and the synced data all reside on an external USB HDD, this keeps the amount of writes to the SD card low and helps avoid issues down the line.
It's also endless tweaking and managing of conflicts.
Also it might work out for people on the free Dropbox plan, however I've got over 350 GB of files in Dropbox and growing. Dropbox makes this easy especially with their Smart Sync.
With Syncthing you'd either keep them on only one computer and risk losing those files, or you'd synchronize that 300 GB on each computer you have.