Google says that the new design will make it easier to "know just where to touch to get directions, recommendations and imagery." Place cards have the new color scheme and icons, and items will slide in and out. Of course, the update isn't all about the visual changes, there are a couple of nice new features. First is OpenTable integration (for US users), which will allow you to make reservations at a restaurant directly in the app. There is also better Uber integration; so, if you have the Uber app installed, you can not only call for a car, but see an estimate of the pickup time and cost for the ride, in addition to how long it will take to get to your destination.
Google says that the update should be rolling out in the next couple days to both Android and iOS.