Put simply, Guice alleviates the need for factories and the use of new
in your Java code. Think of Guice's @Inject as the new new. You will
still need to write factories in some cases, but your code will not
depend directly on them. Your code will be easier to change, unit test
and reuse in other contexts.

Guice embraces Java's type safe nature, especially when it comes to
features introduced in Java 5 such as generics and annotations. You
might think of Guice as filling in missing features for core
Java. Ideally, the language itself would provide most of the same
features, but until such a language comes along, we have Guice.

Guice helps you design better APIs, and the Guice API itself sets a
good example. Guice is not a kitchen sink. We justify each feature
with at least three use cases. When in doubt, we leave it out. We
build general functionality which enables you to extend Guice rather
than adding every feature to the core framework.