Maven can be run straight out of the archive, once the systempath variables are set. Following the 5 minutes guide, I created a 'Hello World' app, compiled, tested and finally packaged it into a jar. Going further, using 'mvn eclipse:eclipse' allowed it to be imported into the Eclipse IDE. There is also a plugin available for tight integration between Maven and Eclipse.
Dependency management is one prime reason for using Maven. The dependencies are downloaded from a remote repository and stored in a local repository that Maven creates. So for several projects, there will be only be one dependency copy. The default remote repository can be changed to an internal repository that will house a private copy of dependencies.
In regards to Ant, Maven makes for a more standardized build process, with little or no configuration needed to start creating, building and testing projects. It provides a common directory layout for each Maven project, easing orientation.