In addition to Arq, I run a local time machine and backblaze.
Backblaze runs all the time on _everything_ (some 4TB), and I have Arq running nightly on my most important stuff (photos, documents, music, recordings) to AWS as well as Amazon Cloud Drive.
If you happen to have critical virtual machines or disk images, make sure you back them up elsewhere, since Backblaze doesn't back them up. Made it an annoyance for me personally, but it otherwise works rather well for the typical user.
Backblaze backs up my virtual machines... You just have to remove those file types from the exclusion list (where they are by default), and raise the max file size to "No Limit". Neither of these are hidden options.
I'm on a Mac - I use Dropbox (with permanent version history turned on) for common files, and Time Machine to a Drobo for short-term versioned/incremental backups (short-term because the backup invariably gets corrupted every year or so and I have to start over). (I also currently use Crashplan but am thinking of switching to Arq since Crashplan has very slow upload speeds - slower than my ISPs upload speeds.)
I'm also figuring out a way to remotely have a mirrored boot drive for my Macbook but haven't quite gotten there.