After using Guice for a little while, I've started learning how to use it better. I can use @Provides methods to configure objects. I like being able to install() modules for modularity.

For webapps, I can have two web.xml files, one pointing to one configuration, and another pointing to another configuration, such as a test configuration, by specifying the different configuration classes as the listener in web.xml files, where the bindings specify different implementations.

I'm not sure if I like the fluent interface. It's nice for reading the code, but it makes referring to the javadoc more difficult. It also creates a bunch temporary objects, but that isn't really a concern. Guice is supposedly a lot faster than Spring, and the temporary objects probably can be optimized away by escape analysis.