The rounded edges and mostly aluminum back on the 6/6+ really remind me of the original iPhone.
I can definitely see some original iPhone in the 6/6+ design. Also, the 6/6+ design really follows the aesthetics of Apples other current products, the iPad and MacBooks, I think the iPhone 6/6+ is really the most premium looking iPhone. Models before the 6 sort of followed the same cues, and they finally strayed away from it. It was bound to happen. It still looks like an iPhone though, I just think the fit and finish is a lot more high end flagship looking, despite how much I loved the 4/4S glass slab design.