Cool. I've been using croc lately to move files around, but this differs in that they are supplying temporary off-site storage so that the host doesn't have to remain online.
Oh I see. syncthing is more for keeping 2 directories synched between machines. I guess in a sense, it's more of a Dropbox competitor while croc and sharr are for one-off file transfers. For awhile, I ran an owncloud server at work for internal use. It was pretty good for file synching, but required some port forwarding through the router. These solutions mentioned here seem to all have a public host somewhere to eliminate that need.
Yes, Croc is AFAIK the best alternative, no man in the middle, but if you can't be online for the downloads, the best is Sharrr, anyway lightyears better than Dropbox or similar big company crap.