I've been using BackupPc for quite some time to backup the home network computers on an external disk.
BackupPc offers a nice Web interface which allows retrieving of files from the backups, in the case of an accidental deletion, for instance, which is quite user-friendly. Apart from occasionaly restoring deleted files, I had never had to restore a backup.
I was more or less annoyed by the processing power needed by those backups over and over again (the external disk on which I'm saving the files is quite slow although connected through firewire, and some of the machines are a bit old and don't like the compression, md5 and other computations needed by the backup process)... and even though there's a differential backup mechanism for only saving full backups from time to time, the length of the backups and the slow down and noise of the disk were recurrent annoyances :(
But two days ago, I've had the assurance that all this was worth the game, since one of the disks on which I had saved more or less all my data suddenly broke down :(
I've had to buy a new disk, but I've been able to restore more or less all the files quite easily (using command line and tar format instead of the web interface), and I'm back on tracks with only one day of email lost.
So thanks a lot BackupPc, even though you make my computers slower and more noisy !