Thank you, Ztcoracat.
I will look into these recommendations.
Before you replied I stumbled upon a non-commercial backup called Duplicati (
http://www.duplicati.com/news) and installed the latest build, 2.0.0.81. I like it so far, but I've yet to test restoring anything.
I thought I was in trouble with this client today. They were missing some folders from their shared drive and my Deja Dup backup offered a blank list of versions to restore despite the folder being deleted only in the last 12 hours and having nightly backups for weeks. Only then did I realize how badly I needed to browse the backup and see what was actually there. I don't trust it now. I restored the entire Deja Dup backup to a temp folder and the folders in question were still missing. But I recalled that in my Zentyal server's shares I had enabled the recycle bin option. I was able to point my client to the accidentally deleted files, show the timestamp to indicate when they were recycled, and avoid dealing with the backups at all.
I'm still very interested in advice for best commercial-grade backup solution with good GUI. Open-source/free or not. BTW, I'm just wanting to back up a single server which ~15 workstations connect to. It's a small business, not a large enterprise. I've seen solutions out there like Symantec Backup Exec for >$1000 designed for backing up entire networks. I'm not looking for anything like that!
Thanks again!