A couple uses, but the primary purpose is as a VM host and file server. Hyper-V for the VMs, and Storage Spaces with ReFS for the storage.

My current build uses a core i5-4570s, but I'd love to have more cores & threads for running additional VMs. My use cases don't require _real_ server hardware (IPMI is overkill), just the ability to run a good amount of test and lab environments.

I'm not the op, but running a TOR node, some Minecraft servers, and some web apps will occasionally bog down my old FX-6300 server. Having a low power part that can do the same work is appealing.