Don't neglect to keep one of your copies off-site. (Here is a tale of woe about having all backups in the same place.)
Personally, I know I would not maintain an off-site backup. In other words, I would procrastinate so that in general, I would still have months of my recent files at risk. So, I use this cloud service as my off-site backup.
I'm still on the fence about an offsite backup for my photos. I'm not a professional photographer and I never will be. This is just a hobby for me. The way I see it, If something were to happen that killed all three of my backup copies, I'd have far more pressing matters to concern myself with.