Obviousness of design patents

Most of our focus in class, especially as engineers, is on utility patents. However, we often hear about design patents as well in the smartphone patent wars. One example of this is Apple's design patent on a rounded rectangle, which was discussed during the lawsuits between Apple and Samsung. At the time, many tech commentators mocked Apple for filing a patent on something so "obvious" as a literal rounded rectangle.

Without have much knowledge about design patents, I imagine that design patent obviousness would differ from utility patent obviousness. We know that a utility patent is obvious if it is obvious to a person having ordinary skill in the art based on prior art. But does the same apply to design patents? Are design patents more like trademarks and about protecting brand identity than encouraging (non-obvious) innovation?

In MRC Innovations, Inc. v. Hunter Mfg., LLP, the Federal Circuit reiterated that the same obviousness standard  used for utility patents applies. If a claimed design is obvious to a designer of ordinary skill who designs articles of the type involved, it is obvious. In the case, the Federal Circuit upheld the district court ruling, concluding that the difference with prior art was a "de minimis change that was insufficient to overcome an obviousness challenge".

Significantly, this ruling rejects the obviousness test in International Seaway Trading Corp. v. Walgreens Corp (2000), which stated "ordinary observer" instead of a "designer of ordinary skill". As one would expect, this new ruling makes it easier to invalidate a patent on obvious grounds because a designer is more skilled, and therefore more capable, than an ordinary observer.