Do you have Crashplan backing you up to a local drive or to their servers?
I use it both to a local drive and to a local drive on another of my
own machines. Backup to the local drive is reasonably fast. Backup to
the drive hanging off another machine is pretty slow, though it helps
if I'm on the same local network. Backing up to a drive hanging off
one of my machines out across the internet -- is hideously slow. For
the offsite backups, I seeded them by doing the backup to a local drive
and then taking the drive to the remote machine and plugging it in
directly.
Nevertheless, my experience is that even a local CrashPlan backup is
substantially slower than either TimeMachine or SuperDuper!
Oh, and I did try having Crashplan back up to a locally networked drive
(ie. the drive was plugged into my airport extreme and mounted over the
local network) - and it basically made the computer unusably slow. I
mean, so slow you'd click the mouse, and five minutes later, the click
would register. Not sure exactly what caused it to be so hideous like
that, but the upshot is that it's really only useful when the drive is
plugged into the computer actually running Crashplan. I'd been very
happy having TimeMachine go to an airport extreme-mounted drive and had
similar hopes for CP, but ultimately I relented and got a Drobo and
plugged it directly into the desktop machine.
None of my backups goes to Crashplan's servers. They all go to my own
machines - local drives attached to desktops on two sites.
It's not my primary backup by any stretch. But it is by far the
easiest way to keep an up-to-date offsite copy.