As long as you're clear on what the HP EliteDesk 800 G1 Desktop Mini is trying to be, it's an excellent machine. It's not meant for entertainment, and it's not meant for graphics-intensive work that demands a lot of processing power.
Easily customizable with toolless entry; very small; wide variety of mounting options; very energy efficient; can handle basic office tasks with no noticeable slowdown; dual-monitor support thanks to two DisplayPorts
No HDMI port; no 802.11ac Wi-Fi; no Bluetooth; noisy fan; a bit expensive; lack of optical drive could still be problematic for some