I currently switch back and forth between a Logitech Dinovo Mini and Lenovo N5902. Both of them have acceptable minimal keysets, though I would really like something bigger with proper keys. Both of them have sufficient key sets.
For a HTPC, my ideal media keyboard would have a 60% layout with dedicated arrow keys, sort of like this http://imgur.com/q3SfrH7
. Being able to ctrl-alt-del is necessary. If you would really like, I can give you a key by key list of what I think is absolutely necessary.
Some things that would make it better compared to the aforementioned 60% layout, but aren't strictly necessary.
-Backlight that turns off when the keyboard is idle. Configurable timeout would be a very nice feature.
-Some sort of "media" toggle key that would turn the arrow keys into media up, down, left, right keys, turn some of the keys into media keys (play, pause, stop, etc), and disable back light for everything but the the media keys.
-A Thinkpad like keyboard nipple with mouse buttons below the space bar would be ideal. Alternatively, a thumb sized trackpad on the right (The thumb trackpad on the Lenovo N5902 is acceptable (http://www.engadget.com/2011/10/06/lenovo-n5902-ditches-the-fingerprint-magnet-finish-adds-backlit/
) with mouse buttons on the left would work. I think good mouse control can really turn a good media keyboard into a great one.
-dedicated Pg Up and Pg Dn can be nice.
-a sleep/wake key would be nice.
-The ability to access F1-F12 through a function key is nice if you want to use the board to configure the bios. None of my current media keyboards have function keys. I plug in a full keyboard when I need to do this, which is very rare. F keys wouldn't really affect my purchasing decision. Other things are much more important to me.
-The ultimate media keyboard would also have a programmable IR blaster for controlling TV, Receiver, etc, but that seems like something of a pipe dream.
Guru-Board seems to have the most minimal acceptable layout (still not wireless). http://www.guru-board.com/english/layout_en
. This layout has all the required keys, as long as there is a way to Ctr-Alt-Del. A wireless version of this would be acceptable but I think a slightly bigger keyboard might actually be better because it will likely have to sit on your lap. If it is too small, I don't think it would sit nicely on a lap.