I hope that I am not posting too late ...
I generally stay away from any product that has "fancy functions". I think that a keyboard should act as a keyboard, and do it well. I think that you should concentrate on good engineering, and good usability engineering at that!
Innovative features that improve usability would give you more positive attention in the press than flash.
I admire keyboards that have the space-saving layout where there are no separate cursor keys and the numeric keypad is overlayed with an inverted-T layout in cursor mode -- the same cursor key layout that most people are used to. Yes, this means that the '0' key is small.
If the keyboard has chiclet keys, then the unused keys (1,4,5,6,3) could be sunk to be flush to the base during cursor mode. If there is backlighting, the inactive keys could have their lights switched off.
If you do select to make chiclet keys, please make sure to do it right:
- Enough space in-between the keys. Rounded corners help.
- Textured key surface for good friction
- Concave key tops are also important for feel
- There is no point of having chiclet keys without scissor switches.
- Scissor switches are sensitive to dirt and grime. Make sure to have a proper "skirt" on each keycap to minimize the gaps where dirt can enter under the key into the switch mechanism. (I believe that this was the major reason why Apple chose to use chiclet keys)
I am also a fan of the Caps Lock key of old Apple and Commodore computers that was an actual toggle switch that stayed pressed until it was released. Then you could actually feel which mode the keyboard was in, and you wouldn't have to look.
This could be a bit difficult to engineer with the current PC standards, though, as the key's state is controlled by the host computer and not by the keyboard.
Myself, I have my Caps Lock key mapped to Ctrl and I never use the numeric keypad.
I would like my next keyboard to have an integrated USB hub, so that I don't have to reach under my desk whenever I want to (dis)connect a USB stick or camera.
As a general rule, I stay away from any product that has "multimedia keys", translucent plastic or my nemesis: the blue LED. There are nights, when I break into computer stores, steal everything that has any pulsating, irritating blue LED in it and then burn them in a ceremonial bonfire in a clearing deep inside the forest ... or maybe not. Only you can prevent forest fires ...