That's exciting, and something I might be interested in. My question and concern, however, is that Tahoe-LAFS seems better suited for distributed storage among unreliable nodes. I consider rsync.net to be fairly durable storage, especially since the way I use it is as backup and not the only storage location for a file. I have the same question about using S3 as a tahoe backend, which is another thing I've seen.

Of course, you could just use Tahoe-lafs to store everything on one or two nodes when they're reliable and durable, but then why not just use gpg or encfs, which don't require custom clients or gateway/introducer nodes?