Not Underwhelmed, but "depressed" for a moment...
First, Do not like the "space grey", but thought the iphone 5 "slanted black" was the perfect color and look..finally perfection like the Macbook Air in esthetic design. But...
After being "depressed" for a few minutes because I "have to buy" a new iphone..
Quick story: I moved out of the country after paying off my iphone 5 after 4 months from t-mobile...finding out that in Japan none of the carriers will sell me a nano-sims card "unless" it has a logo on it "stating" that it is a Japanese iphone (contra to all of the post stating likewise on MacRumors).
I went to all three carriers (including Docomo) and Docomo after 6 hours arguing with them insisting that my phone worked on Japan's system as the other two carriers stated that it would not (including after going to the Osaka Apple store and they said that Docomo would sell me a chip - this was before the announcement...), I finally got them to at least put a nano-sims into my phone (the other carriers would not by law) and it indeed worked...but the Sales Rep. said that if he sells me the nano-sims, he would be fired because it is against the law in Japan to sell me a sims card that is not for a Japanese phone.... Japan does not even unlock their phones after payoff or allow non-Japan iPhones on their system by law....I was mad....
All that said after paying over $600 after four months having to buy another iphone, I was first "depressed" about the non-full black iphone 5S, but looking at my current iphone 5 only after four months of babying it noticed that the ionized paint near the borders "are" in fact starting to fade just a bit...
So, the reason for the color change may not be necessarily a cosmetic change for change sake or to save money, but maybe a necessity. Notice that they are going with chrome edge (non-painted) on the "space gray". I understand if it is a necessity, but thought the "Slat Black" iphone, which is Steve Jobs last input design wise...was indeed perfection.