Pro: they avoid starting another instance of the JVM for each "command"; they run on Windows.

Con: they are grotesquely bloated for humans to read and write; (as indicated elsewhere) they make any custom file generation "tasks" a PITA.

Personally, I'd like to strangle the bastard that invented Ant :-)

It would have been so much nicer to have just copied make syntax, and predefined a few macros for java-specific tasks which actually spun off threads within a JVM based interpreter.

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Xml is an awful language to program in and every ant file grows with the software it builds => ant files that take more than 2 screens are very rarely maintainable.

Ant doesn't conditionally re-execute a recipe when the prerequisites are newer than the target. Such logic isn't needed for Java projects since it is built into javac. Hence Ant is okay perhaps for Java projects but inefficient for others.