The main issue we hear when users complain about the current collection of GPS apps on Windows Phone 7 is the need to rely on a data connection.
GPS Navigator aSpass solves this issue by providing map caching, allowing users to download portions of the map for off-line use.
The app provides the now nearly standard turn by turn voice directions and also automatic route recalculation, walking and driving directions, map rotation, Bing and OSM maps and also English, Spanish, Italian, French and German support.
All that for only $4 sounds like a steal and with 4.5 stars in the review section the free trail hardly sounds necessary.
GPS Navigator aSpass can be found in Marketplace here.