I wasn't very interested in Glacier at first, but the more I hear about it, the more I'm convinced it's a perfect companion to time machine backups. Why pay $13/mo for CrashPlan or some other similar service when I can pay a fraction of that for Glacier?
Of course, this makes sense for me because my backup is rather tiny (~300 GB). The "unlimited" plans at backup services are worth it in certain scenarios I guess.
Note that Glacier+Arq also allows you something entirely different from CrashPlan and incremental backups: Data archives. I.e. you can store data there cheaply that you don't have to keep available on your hard drive. Very useful for storing data that's too large to have on your drives all the time, like the pictures and videos mentioned in other comments in this thread.
Crashplan is cheap b/c they make it quite difficult for the average user to _actually_ backup all of their data. The interface is all sorts of confusing to non-experts, and I was embarrassed to realize I had fallen for a UI trick that made me think my drive was backing up, when in fact it was only my user directory. I'd made the same mistake on the 6 computers in the family, and had to do a bunch of phone-tech support with in-laws.
I paid for a year, so I'm using it now as additional backup, with my primary backup on a local HD and Arq.
Of course, this makes sense for me because my backup is rather tiny (~300 GB). The "unlimited" plans at backup services are worth it in certain scenarios I guess.