Steven Aquino:

From a pure design perspective, aesthetically speaking, it’s perfectly reasonable to criticize the new shapes. They are indeed ugly, but the overall importance of this new addition trumps the way in which they’re presented. That is to say, regardless of how the buttons look, the sheer fact that they add a level of desprately-needed contrast makes the buttons a huge usability win, and likely — rightfully — will garner much praise from the visually impaired segment of the accessibility community.

Designers need to remember this when criticizing the new button shapes.