After downloading the free app from the App Store, you'll have to sign in to go any further. Don't be fazed by this extra step, as there's a very good reason for it. Once you sign in, you'll see any previous searches plus integration and custom maps.
The interface is clean, simple, exceedingly user-friendly. There's a field at the top to search for locations or addresses, the main map windowfront and center as you would expect, and a tab in the lower right that slides out so you can choose layers. The layers section pops in from the right to let you toggle traffic, public transit, and satellite views, and it offers a link to the Google Earth app for 3D views and other features (more on that in a minute). And once you tap on an address or location, you can jump right to Street View without leaving the app. It takes a couple of tries to figure out how to get there (click on the related photo), but you'll remember after you do it the first time.