Couple days back TA completely overhauled their mobile app with a new version that is sure to be a game changer in this category.
The most impressive new feature is that a lot of TA's content is now available off-line via new "city-packs" which you download before you leave for your trip.
The best part is that each pack includes a full Google city map of your destination which is more detailed than the maps you can download from Google's own app. Of course these maps have GPS functionality, and major landmarks listed.
The packs also include the most recent reviews for restaurants, hotels, and attractions...all available off-line and complete free!