I used to backup with Arq to S3 and the restores were very fast. With Glacier, Arq initiates the data retrieval and waits for file availability in the UI. Glacier can take a day or so, laptop needs to be open and connected to internet during the time for the transfer to complete. Given I'm primarily backing up external drives, I find this UX not an issue, but if you wanted backups with instant accessibility, backing up to S3 really isn't that pricy.
