Repository pattern is used to abstract from particular database and object-relation-mapping technology(like EF) used. So I can easily replace (for example) my Entity framewo
One of the new features in Entity Framework version 4 is "Code First" development. This will allow you to use regular C# (POCO) classes with entity framework. Once your classes are written this way, you could write a different implementation of the repository that persists those classes using a different mechanism.
ScottGu has a blog post containing more information.