I currently run my HTPC on a 2011 Mac mini 2.7GHz Dual-Core Intel i7. The original builds were on 2011 Mac mini servers, but I was trying to deal with a WMC issue and the servers were much better at encoding. Anyway, the HTPC role is essentially a server as its on 24/7, runs headless, RDP, and clients (Xbox 360 extenders). As a HTPC, storage space is very valuable and I can't have too many external drives hanging off. Therefore, I run it Windows only. I did save the original hard drive with OSX and connect it via Thunderbolt or FW800 for firmware updates.