While it is a standout, it is ridiculously expensive. Art Lebedev wants $2068 for the Optimus Maximus.
However, there was a patent filed by Microsoft that could have a similar functionality for considerably less money: The company's "interactive keyboard with a viewable display" was submitted as a patent in September of 2010 and published by the USPTO on March 22, 2012. A second supporting patent extends the patent with the option of "multiple different key arrangements".
The differentiator to the Optimus Maximus is the fact that the keyboard uses only one display that is integrated below "at least partially see-through mechanically depressible keys". The problem of this approach may be a limited viewing angle toward the keys as the display is located below physical keys and it may be challenging to achieve a high usability factor in such a device.
If Microsoft can, in fact, build such a device and offer it for a reasonable price, such a keyboard may be the most significant evolution of keyboards in decades and tide us over to a time when haptic touch screen keyboards overcome their latency problems and turn into useful keyboard replacements.