This is a solid HTPC keyboard, lightweight with good overall size. The newer white one looks a bit better imo without the crazy touchpad "flair" lines, but it also doesn't drop in price as frequently as the original black one. The black model is frequently on sale for $20-25 from Newegg, Amazon, and Staples especially around the holidays. Not great for typing, but very functional for HTPC use.
Some other good options for HTPC use:
1) Lenovo N5902: Frequently goes on sale for $30-$40 from Lenovo. Kind of a hybrid trackball, BlackBerry typing remote-control experience. The optical thumb pointer is a bit jittery imo, but overall this device works well for those who want more point-click browsing and need less typing.
2) Logitech TK820: much more expensive but much nicer build quality compared to the K400. Feels better overall from typing to using the touchpad, but costs about 3x as much. I'm personally waiting for this to go on sale for $40-50 during BF. Newegg just had a deal on refurbs for $45, but who really wants to buy a refurbed keyboard?
I've been using the K400 and N5902 along with a cheap Windows remote for a few years now on my HTPCs (and now an Intel Haswell NUC) and I use them all depending on context.
One thing to keep in mind with this K400, it has terrible range if you connect the universal receiver directly to the NUC unit. May be some kind of EMI or shielding problems when it is that close to the chassis, but I had to use a USB extension dongle to move it away from the NUC itself. Symptoms will be really sporadic/unresponsive mousing and typing, as if the keyboard is defective (or drunk). Some reports on Logitech forums confirm the issue and acknowledgement by Logitech staff.