Jungle Disk online backup with Amazon

Poking around for an online backup solution, I found JungleDisk which allows you to backup your data to Amazon’s S3 storage service for $0.15/gigabyte/month. The client is available for windows, mac, and linux. Has anyone used this? It seems almost suspiciously cheap (although right now you’re only paying for the service from Amazon; the program itself is in beta.) And I’m not that fluent in cryptese, so is the encryption all legit?