Western Digital's My Book is the closest competitor to Seagate's Backup Plus, and the My Book tops out at 6TB. There are a few other competing storage solutions. Many lack certain software features, and none go as far as Seagate or Western Digital in adding significant value beyond simple backup tasks.
As a result, the Backup Plus doesn't give us anything to complain about. It does what it's designed to do, and we didn't run into any idiosyncrasies during testing. We don't love running two cables to an external peripheral, but until USB 3.1 really takes off, we're stuck with a dedicated connection for power.
Hard drives are commodity products, even though there are just a few companies still building them. To make an external drive stand out, its software features have to enhance the total package. Seagate does a good job of delivering an array of software-based capabilities that transcend the local PC, touching the social and mobile segments. Some folks will value these features; others won't use them. But I'd go so far as to say this is the benchmark other local backup solutions should be measured against.