The "ergonomic" Motorola keyboard really has nothing to do with decent ergonomics. Look at your hands. When holding a Qwerty phone between your palm bottoms, your thumbs do not move in the direction of the curved key rows of the Motorola keyboard. So it looks that it was designed by an arts designer and no expert of ergonomics. Besides, it and the blue keyboard are examples of English-only keyboards which are more or less impossible to localize to other languages - there are too few keys.
For some tablets are available virtual split keyboard where the key rows are matched with the natural thumb movements: on circular arches, the centers of which are near the corners of the tablet screen. But those keyboard substitutes cannot be called ergonomic, because of other reasons, such as the fact that its keys are only virtual keys on a touch screen.
But does the 4 or 5-way rocky key in the center of the Motorola keyboard make its ergonomics acceptable? Hardly. I've found it a lot more natural and easier to use four arrow keys than streching my thumbs a quite long way to the center of the keyboard. Besides the use of 4 arrows keys is a more standard way: they can be used like on full-size keyboards.