I received one of these NUC's last year as a test unit. Great little units, sits neatly behind monitors. Although i found it lacked a sound card, USB ports and cheap storage options (at the time).
I had the exact model as you but i swapped it for the model with Ethernet and Dual HDMI ports (No WiFi and Thunderbolt port on that model though). Never had any issues with overheating, it barely ate up any power.
Did you get the surprise Intel jingle when you opened the box?
