想了解Flex 4 预览版特性及怎样迁移Flex 3 应用，可以关注一下这本书。

1. New SDK Features
2. New Flash Builder Features
3. Working with data and services in Flex
4. Migrating Flex 3 applications

链接：http://livedocs.adobe.com/flex/flex_4_featuresandmigration.pdf