I'm a Backblaze user, became one right after another post from their blog hit HN front page about 8 months ago. Backblaze almost saved me once when my external HDD died due to dropping—the reason it didn't actually save me is because initial backup wasn't yet completed (not their fault). Otherwise I could easily order from them a new HDD with restored data, which is a very nice feature.

Sadly their OS X client is kind of quirky—I'd rather have a command-line one that required hand-editing configuration files (I'd wish for something other than XML though), but which would run more reliably and transparently.

(Currently it shows “Computer Missing” and says that I haven't backed up in more than 2 weeks, though I did actually press Backup Now quite a few times in past few days. There're some other oddities in behavior. I suspect I'm back into “searching for decent online backup solution” mode lately…)