The TypeMatrix is an awesome keyboard. I just wish they made a Macintosh version of it. I really use the Mac keys a lot. I'm currently using the Kensington keyboard with all the Mac keys. I don't know how I every got by without the iTunes keys.
Command, Sleep, Volume, Eject are all must have keys while on the Mac platform. Yeah, you can do it all with the mouse, but I hate that damn thing.