Tim, over the LAN the difference with SSH is noticeable. Over the WAN, max upload is 1MB (actually quite good in this area), therefore the speed reduction using SSH is a non-issue. Load balancing on an upstream single pipe like this doesn't work, therefore we can only use one WAN connection at a time.
Thankfully, the sync has worked very reliably, every day for the last 18 months or so. The email notifications (only after share backup failure) have worked 100% too. The only time we've seen failures is self induced...like not forwarding ports correctly etc. I also wasted a day in pfsense because the receiving NAS DNS gateway was set to an incorrect IP. The DNS issue is a sneaky one because it does not affect local NAS access....but it sure messes up outbound WAN traffic from the NAS.
For the record, our READYNAS unit is quite happy rsyncing to QNAP too.
Steve, with the correct port forwarding, rsyncing would work using the free Deltacopy rsync software (no NAS required). The reason I'm such a fan of rsync is that is incredibly efficient in terms of data that is transfered. It only transfers binary differences in changed files...never the entire file (unless it's new). Therefore typical rsync times after say a day of busy email, typical business use etc. are typically 3-5 minutes/workstation. Using SSH, data is also encrypted in transit. Pretty amazing.