Wayper (free today only, then US$1.99) is a map app designed to avoid data charges by letting you download detailed maps of 27 cities worldwide.
In the U.S., that includes New York, San Francisco, Los Angeles, Sacramento, San Diego, Chicago, Washington, Boston, Buffalo, Rochester, Pittsburgh and Las Vegas. You can download just the maps you need. Internationally the app supports Paris, Berlin, Amsterdam and more. There's a complete list at the App Store.
You can search for an address, a point of interest, or an intersection. In my testing, the app responded quickly. When plotting a travel route, Wayper provides several options including bus and pedestrian routes. If you zoom in enough you will see 3D outlines of buildings, and the renderings are speedy when you rotate the map to change perspective. Although not stated on the app information page, it is really designed for walking and transit directions. There are no time estimates for driving, which seems a strange omission.
Wayper is missing is any GPS connection, so it doesn't know where you are. You must set up your current location and then your destination. (Note: the developers say the app does show your location, so with an associate we tried again. One time the GPS marker was there. Another time it wasn't. It's hard to know exactly what happened, so I'll give the people behind the app the benefit of the doubt.) The map draws several possible routes with time estimates. But once you get going, there are no turn-by-turn directions. In addition, while the app has a large POI database, other than the name of a place there is no further information. And your contacts list is not attached, so if you are going to someplace in your contacts you will come up empty.