It's very useful for recording programs, and transferring them to your PC, as well as downloading any Kodi programs, to view later, or if the stream keeps freezing.
I'm regularly using mine, in my VU+ Duo 2, but I had several old hard drives, from various old PC's, lying about, that were suitable.
Given how quickly, and easy, you can install a hard drive, in the VU+, I'm surprised most owners don't do it.