I was working on Spring 2.1 stuff this week with Joris. We were preparing a sample using all three ways of doing dependency injection. The sample does not only highlight dependency injection, but also features a back-end based on Hibernate.
Several features in Spring 2.1 require the ASM byte code manipulation framework. Hibernate also uses ASM, through CGLIB. There is a binary incompatibility between ASM 1.5.3 and 2.2.3. The former is used by Hibernate, the latter is used by Spring in various scenarios; specifically in some of the AOP functionality and the new @Autowired features.