It is definately worth the time to learn. I have moved all my projects over to Ant now, and no longer use the built-in build facilities of any IDEs, batch/script files or whatever.
There are two tools which have greatly improved my productivity using Java, and they are
JUnit and Ant. Both are free and Open Source, and I would recommend anyone who wants to write good, reliable java code, fast, to spend a few days learning how to use them.