I don't think you know what the term means. Ground up means they started from scratch. It's radically different from iOS 6, and hence it is built from ground up. It's always relative to your last product. FIFA 07 was built from ground up with a new engine, even though it looked similar to PES 7.
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All smartphone platforms borrow from each other.
Android copied from iOS for years, but forum members saw that as Android catching up.
Windows Phone comes up with a fresh UI that borrowed from iOS (navigation, transitions, restrictions on file transfer, tight grip on updates), but will now get a notification centre, among other Android features. No one's complaining.
So most of this "Android rockszszzzz" crowd will whine about iOS showing signs of age and will whine when they borrow from others to evolve. Nice.
I know iOS and Apple are facing major challenges. Google is getting better at products far faster than Apple is at services. Apple Maps is still woeful in India. Siri isn't as good as Google Now. Those are valid criticisms. I'd like to see more of that and less of this whining and general fanboy trash.
Now with the exchange offer for iPhone 4, many people in my office have bought it for 19k and most upgraded from Android phones. I don't hear a single complaint about the phone from them. All are very happy with a three year old iPhone. These users are not tech savvy at all, and they will love the new iOS when it launches, I'm sure. Every other week someone in office comes to me and says that their Android/BB is slow and hangs. One guy's Xperia Z has become laggy, and others have pretty decent Android phones (10k and above). Two of my bosses have iPad 1 and 2 and a third is using iPhone 3GS. Both are running smooth even now, just like the iPhones.
For these Android users, clearing up the internal memory, cache, and other nonsense is cumbersome. They don't want to do it and I don't blame them. Phones should just work. I don't see that happening with Android yet. Even WP8 is getting there, and to some extent Nexus 4 is too. Not the rest of the Androids though.