tl;dr: a cheap data archival solution; upload is free, storage is cheap (€0.002 / GB / mo), download is somewhat less cheap (€0.01 / GB) and not instant; rsync / sftp IS supported for upload, but an API call is needed to complete the operation.

Seems great for redundant regular backups that you hope to never restore from, but would like to keep just in case.

(EDITED: previously incorrectly stated that rsync and sftp are not supported.)