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I don't own an Android and so it was interesting seeing this collection of images arranged side-by-side for comparison. To my eyes, my first impression is that the interface peaked around version 2.3. The 4.x series looks too low-contrast and transparent for my taste. The 2.x series has a nice, strong contrast and firm colours and that appeals to me. Were I selecting an OS based on looks alone I'd go with Android 2.x.