You should try a partial restore to see what the problems might be. There are many negative posts, but some are several years old.
http://mozyrestore.com/
My experience tells me this:
No file is safe on a hard drive. They crash, the cases malfunction and they're vulnerable to fire, theft and the whimsies of God and Satan.
I've been experimenting with Gladinet, which os an interface for several online backup service (Google Docs and MS Sky drive included, as well as Amazon).
It's a manual process, but I find Google and MS more trustworthy than most.
http://www.gladinet.com/
The only safe answer, IMHO, is lots of copies in different formats.