I currently have iPhone 5, rMini, MBA 11", and MBP 17": - 17" as desktop replacement, for programming, video and photo editing, iTunes library, and other desktop-class tasks - 11" for programming on the go, fits in my Scottevest jackets, or carry it in a shoulder bag for iPad - rMini as a wearable computer, fits all my cargo/hiking pants and shorts, goes with me everywhere (taken to the mountains already!) - iPhone, well, is a phone + WiFi hotspot for whatever other devices I have with me, email on the go, Yelp, navigation and various other small tasks After retina MBP 13" introduction, I'm thinking about replacing 17"+11" with 13", since maintaining and syncing 2 computers is too much. And I hope that iPhone 6 will be 5". I think, I'll feel complete with 5", 7.9", 13.3" range - it covers everything I need without gaps too big or too small. So, this and the endless debates "Air or Mini?" here got me thinking about ideal screen size "spacing". And sure enough, the ratio 13.3/7.9 equals 1.68 - very close to 1.618, the golden ratio (within 4%). And by this theory, the ideal size below 7.9 would be 7.9/1.618 = 4.9", or exactly what Tested.com thinks will be the size of iPhone 6, since it's the same sheet as Air (254ppi) cut at 1136x640 resolution. If you prefer Air, the harmonious step up would be 9.7*1.618 = 15.7" (15.4" rMBP), down 9.7/1.618 = 6" (iPhablet rumors, anyone? ) But having both Air and Mini is too redundant (a mere 1.23 ratio), and 13" MBA or MBP with Air is only 1.37 step, let alone 11" MBA: only 18% from Air. Anyway, thought I'd share my thoughts on how to cover the range of screen sizes in a way that feels complete and satisfying without redundancy.