This app is the best Ive found for offline use of Open Streetmap data, especially for outdoor and travel use.
Easy to download just the area you need, and small because its the vector data not image tiles.
Height data used for both contours and height profiles (watch their video, and try holding two fingers on map). 3D tilting mode very useful for seeing the shape of the mountain.
Beautiful and fast, Apple meets Swiss cartography. Well worth the cost, cheaper than one paper map!
Version 3 lets you save waypoints, and draw tours with your finger, without adding excessive clutter. (Easy to import gpx/kml tours too.)
Limitations: Does not offer satellite views. OSM data is good in many places, sometimes the best in out of the way places, but generally not as good as say the French topo maps.
And it still nags you about Airplane mode, even though you can now use GPS with this on. (But after you dismiss the message, it does work.)
improbable22 about MapOut, v3.0.3