My experience has been pretty good. In terms of functionality they both effectively do the same thing, but the one thing that makes Resilio Sync slightly nicer than syncthing is that I can just give out key for directory that I want to share - similar to a torrent magnet hash. Whereas with syncthing I have to connect and allow multiple devices together in order to sync between them - with Resilio Sync I just give out key and device can start downloading/seeding content. That may not be a big deal if you have a few personal devices, but if you're distributing files with a number of devices you don't know (as you typically do when torrenting) then you can just leave key out for anyone who wants the content.
As an added bonus, compared to a traditional bit torrent client, Resilio Sync allows you to update the content in a given directory and the users in the swarm will also get the new content without any additional work.
So far myself and a small private community are using it to archive about 2.5Tib worth of data that continues to get regularly updated - never once had an issue.