Arq lets you cut out the middle man by allowing you to backup files to your own Amazon S3 account, in exchange for a one-off license fee. As used by Nylllon to handle around 60GB of data, we can't recommend this highly enough.
I've been using this for around 8 months. It's one of those apps you wonder how you managed without it. It's keyboard-based note-taking, with search and integration with Simplenote. It's a fork of Notational Velocity.