I wish it wasn't a local filesystem. Google Docs was superior (for me) in that my files were available on every device. To achieve that here would require setting up Dropbox or similar and dealing with edge cases. If this API was more sophisticated with conflict resolution, Firefox could sync these files for me (maybe S3 compatible? I dunno) and then every app could have magical Dropbox/GDrive capabilities instead of a boring old tech folder that gets wiped out every so often.