I've been using Backblaze for at least a year with no problems. The initial upload takes forever, of course, but I'm sure it does with all these systems that are designed to upload unobtrusively in the background. I went with Backblaze because I liked how, in the event of a disaster, you have the option of having them FedEx a hard drive to you with all your data on it. If my house burns down, then $200 to get my data back immediately will be the least of my worries.
Hard disk space is incredibly cheap nowadays, and I certainly thought about just buying a couple of extra drives and keeping one rotated out over at my sister's house. But then that's one more thing to keep up with, and once you spend a couple hundred dollars on two drives you're up to the same price as three or four YEARS of an online service. Add that to the fact that I've had the unpleasant experience of losing data, confidently pulling out my backup drive, and then discovering that the backup drive was corrupt, and I think that automatic, encrypted, offsite backup of all my pictures and music and videos is the easiest five bucks I spend a month.