backups with git

Dear all,

I'm thinking of using git as a backup solution for my whole system,  
setting my $GIT_DIR to something like "/backupdisc/backup". Does that  
seem sensible? In his Google tech talk, Linus said that git was not  
good at huge projects; I guess that would apply to backups. On the  
other hand, maybe a backup doesn't need to be as fast as he wants git  
to be for projects. Has anybody used git like this? And was it a good  
experience?

Kind regards,

Roald