No, it's not just a CPU refresh. Apple started selling a new line of iMacs today, and yes, while they have fresh processors and graphics cards inside, that's really the least of it. Going forward, all the 27-inch models have a 5K screen -- not just the flagship we reviewed last year -- while the 21.5-inch version now has an optional 4K panel. Across the board, too, these new 4K and 5K displays have a wider color gamut, although the difference is fairly subtle. Possibly more important than the iMac itself, though, are the input devices: Apple redesigned the wireless keyboard, mouse and trackpad, adding rechargeable batteries and, in the case of the touchpad, pressure-sensitive Force Touch gestures.
I've been spending a few days with the new iMac, and chose to review the 4K 21.5-inch edition in particular since this is the first "small" iMac with a Retina display. Between the crisper screen, compact footprint and a lower price than the 27-inch models, it has the potential to hit the sweet spot for a lot of people. Just be sure to upgrade the hard drive before you place your order.