$0.25 per (deduped) GB/month
It works very nice with iOS for photos and videos and it's unlimited and free. Google rules! :) I love the Webapp and how I can do albums, easy video upload and download from iOS, nice!
The first upload took over a week, but subsequent updates are happening all of the time. On an older PC (2009) I had to move it to daily (evening) backups instead of continuous.
It does not (by default) backup literally the whole machine (although you can fiddle with options to get it to do that). It's set up to do your data (not OS or Applications). It does not provide a bootable clone.
I strongly suggest you also have a full bootable backup locally and treat BackBlaze as disaster recovery. I have a Mac and use TimeMachine -- but anything that makes you a bootable drive (or could restore to one) is fine.