I don't get the obsession with custom keyboard with ever fewer keys. If I designed one, if anything it would have at least a few more modifier keys that a standard keyboard.
I never really got used to using the numpad block, and it's nice to have the mouse a little bit closer. But I definitely use the navigation keys (both the arrow keys and the Ins/Del/Home/End/PgUp/PgDn block), F-keys, symbols (`~[{]}\|;:'",/?), all of the modifier keys, Esc, and PrtSc.