I've recently been exploring how I might use Maven with PHP. Whilst the maven-php needs a little TLC, the main thing that struck me was that by moving to a none-php based build tool (I know, I know, Maven is more than a build tool), I am able to take advantage of so many other plugins such as Cucumber for BDD running on jRuby, YUICompressor on Java, and others. And by using Maven I can throw the POM at Jenkins.
I also noticed that by using a build tool that can do lots of pre-processing for me before deployment, I can create more responsive web apps (e.g. reduce apache re-write rules, version resources such as js, imgs, css as well as minimise them). A consequence of employing such techniques is the production of greener web apps as they use less resources (therefore energy) on a per request basis due to the tools doing the work before deployment.