For those of you who are thinking about using the Mac Mini as an HTPC, go for it! It's a great box for media at very low power usage. I bought the base unit.
My setup:
2012 Mac Mini Dual Core i5 2.5GHz
16GB ram (upgraded from 4GB)
256GB SSD OS drive (using the dual drive kit from ifixit)
500GB (stock drive used as storage)
2x HDHomeRun units (4 tuners total)
2TB MyBook Raid-0 USB drive
750GB MyBook USB drive
Windows 7 64-bit Ultimate
eHome USB IR receiver
Harmony 880 remote
I'm using a mini-DisplayPort to HDMI adapter for the TV (contrast appears to be better compared to using HDMI port). This causes an issue that required a workaround. When the Harmony remote turns on the TV, receiver, and Media Center (configured as an HP Z500 PC), the TV doesn't get detected by the Mac Mini quickly enough so when Media Center loads, it displays at 1024 x 768. This issue does not happen when using the HDMI port.
To get around this problem, I told the Harmony remote to set the "HP Z500 PC" to "MyTV" as the input when it "powers on." The "MyTV" input command is the IR signal for the OK button. Once the Harmony remote is done turning all of the devices on (or so it thinks), I told it to wait 10 seconds and then send the IR signal for the Green button, which launches Media Center. This way, it comes on when the TV is properly detected so it displays at 1920 x 1080.
I also configured the "HP Z500 PC" to power on and off using "different buttons." For powering on, it's basically just hitting the OK button. For powering off, it sends a sequence of IR signals: Green button, DirectionDown, DirectionLeft, OK, OK. This sequence exits Media Center.
According to CPUID HwMonitor, the Mac Mini is using about 12 watts when I'm watching/recording TV or watching mkv files. When it's idle with Media Center closed, it uses 2-4 watts of power. I might hook up a Kill-A-Watt meter to find out how much it's actually drawing from the wall.
As for the performance, everything is as smooth as button including 720p/1080p mkv files. With the concurrent user hack, I'm able to log in and do administration, rip movies, etc.
I haven't tried Blu-Ray content on it yet. I only boot into OS X for EFI firmware updates. Before I bought the 2012 Mac Mini, I was running the same set up with a 2007 Mac Mini (Windows XP Media Center 2005).
Some of you might ask why on earth did I not just build an HTPC. I used to have one with tuner cards and a bunch of hard drives, but it used up too much energy and produced too much heat. It was also bulky, which made it difficult to fit into the living room area.
Here's a picture of my setup:
FYI, the 360 isn't connected. That ethernet cable on the right side of the floor is just temporary.