Attic has still problems for large backups (when the block index gets >2gb). There are also several minor issues due to the tool being relatively new (file selection is lacking). Check it's issues page: https://github.com/jborg/attic/issues/
To work around some of attic's more UI-level shortcomings, I made a wrapper script called atticmatic that adds a declarative config file, excludes file, etc: