I looked into maven about six months ago. We were starting a new project, and didn't have any legacy to support. That said:
- Maven is all-or-nothing. Or at least as far as I could tell from the documentation. You can't easily use maven as a drop-in replacement for ant, and gradually adopt more advanced features.
- According to the documentation, Maven is transcendental happiness that makes all your wildest dreams come true. You just have to meditate on the manual for 10 years before you become enlightened.
- Maven makes your build process dependent on your network connection.
- Maven has useless error messages. Compare ant's "Target x does not exist in the project y" to mvn's "Invalid task 'run': you must specify a valid lifecycle phase, or a goal in the format plugin:goal or pluginGroupId:pluginArtifactId:pluginVersion:goal" Helpfully, it suggests I run mvn with -e for more information, which means that it will print the same message, then a stack trace for a BuildFailureException.
A large part of my dislike for maven can be explained by the following excerpt from Better Builds with Maven:
When someone wants to know what Maven is, they will usually ask “What exactly is Maven?”, and they expect a short, sound-bite answer. “Well it is a build tool or a scripting framework” Maven is more than three boring, uninspiring words. It is a combination of ideas, standards, and software, and it is impossible to distill the definition of Maven to simply digested sound-bites. Revolutionary ideas are often difficult to convey with words.
My suggestion: if you can't convey the ideas with words, you should not attempt to write a book on the subject, because I'm not going to telepathically absorb the ideas.