Just to clarify. I've never had to restore my data from backup drives. I have had hard disks go "funny" on me. This happened on two disks. Files started becoming unreadable some of the time (but not all) and I/O timeouts started happening. In both cases, I copied over my data from the affected disk to a new disk.
I haven't ever lost data as a result of a power outage, partly because I'm a compulsive user of the save button / command. I also didn't get bitten by the ext4 rename bug / controversy because I was using ext3 at the time. I don't have a UPS at home or work.