I received a Diamond/ATI MCE remote (with green Button) for free when i bought my ATSC tuner card from Newegg. I embedded the USB dongle behind the VFD faceplate on the Thermaltake case I used, so it is invisible.
Having had a disappointing experience with the Harmony One and HTPC, I now use a Universal Remote (URC) 200 (probably $30 on flEaBay). I cloned all of the WMC functions that I needed. It has all of the OEM WMC codes, but also does "punch through" to directly control the receiver volume and muting. Plus, it chords macros, so it will turn on and set up the TV and receiver in one shot, just like the harmony units.
I vastly prefer the hard buttons of the URC to the touchscreens of others, FWIW. YMMV.
I found that the effort of making only one remote the end-all for the HTPC was far more expensive and time consuming than the value of having slightly less clutter. I got it down to the URC for movies and TV, an RF Lenovo micro keyboard remote for general computer use and whole-home volume control, and a wireless keyboard and mouse for games or longer computer sessions. All three remain connected to the HTPC concurrently without problems. The three are better for me than any one product that I could find.
Oh, and I also love having an old Griffin Powermate knob that I used to use on my Mac. It sits by my feet, on the magazine shelf of my coffee table. I can roll on or off volume smoothly with my big toe, without putting down my beverage, or tap it with my foot to mute if I get a phone call, for example. So, I guess that is FOUR human interface controllers, mostly hidden out of sight.