Server centric model that makes deploying the backup client to end users convenient, but unfortunately not very reliable.
The ability to take full backups of all virtual machines hosted on a Hyper V server through without deploying the client to all of the virtual machines.
Almost everything else.
The management console is using a very poor performing SQL Anywhere database program (by default) that makes navigating the management slow and clunky. The management console itself is designed fairly well in the latest 2015 version.
The process of adding a new server or workstation takes around five manual steps. You install the client, then you create a group or add that machine to the group, then you add the client to the actual backup task (because the grouping is just there for giggles) and then you edit and make your backup selections. Repeat this process if any mistakes were made.
The process of database backups are cumbersome and slow. I had an incident recently where database backup jobs were stuck in a "Queued" state for over 30 minutes that I eventually called support about and found that this was "normal" for the first run as it scanned the databases, but there was no documentation of this behavior.
You can create useful "media sets" for Tape backups, but no such sets for hard disk backups. The best way to use hard disk for backups in this program is to have one huge virtual (LUN) or physical drive (RAID), depending on your backup sets. If you have 3 separate disk drives setup and you're trying to manage which jobs go to which drives, you are not going to have a good time.
General backup performance is slow for us, but this could be due to our setup, admittedly.
I have not used this program when it was branded Acronis, but from my time with this program and from many other complaints on the web, this was a better product under Acronis.
If you are going to go with Symantec, make sure you set it up with religious dedication to the details. Mistakes are going to give you major headaches.
We use Symantec Backup Exec as our primary backup control process and disaster recovery process for all on site servers and workstations. We have not realized many benefits from this product for the reasons outlined above. We have been looking at alternates to Backup Exec.