I do it, mostly for the email reporting that's built into the system more than anything else, across 2 dozen DPs. You could replicate the entire process for free with rsync, launchd, and some Automator to send the emails using Folder Actions, but the volume cost of licensing made it worth while to implement for us.
Issues you may run into is permissions on the newly replicated share since CCC tries to copy over the same permissions and if you're using local accounts on the DPs even with the same name, technically they have different UUIDs thus you may get some permissions errors. You may need to run a script afterwards to reset the permissions on your DP because your read / read-write accounts may technically have different permissions / ACLs. Remember Mike Bombich was thinking of CCC as a backup tool and permissions would be essential to that, I put in a request for him to at least consider putting in a checkbox that says to ignore permissions.
