Their argument goes into more than just rounded corners. I agree that there were other touchscreen phones out before the iPhone , the LG Prada for instance. However the argument Apple has goes into UI and UX, the skewmorphic design, and some of the details of the device.
While I see both sides, I also see an obvious mimicking of Apple’s design language with the metal bezels, the radius of those rounded corners, the app layout, and even wallpapers. They also (IIRC) uncovered evidence within internal emails (at Samsung) essentially confirming they copied the design.
http://bgr.com/2012/08/08/apple-samsung-patent-lawsuit-internal-report-copy-iphone/.
Like many legal cases, this will set a standard for how industrial design cases are ruled in the future, so, it makes sense for both Samsung and Apple to fight it to the end.
It won’t set anything because Apple has lost several cases for its patents against Samsung outside the US.
All this was about is Apple attempting to kill off some competition. Business tactics.