My current peave is that I can't build Maven locally (I want to make a minor fix to the clover plugin). Not just pulling down the CVS HEAD, but I pulled down a tagged release, the beta-10, and tried to build locally. Crash and burn. The whole point of Maven is that this should not happen, I have the same code as they did when they rolled out the beta-10 distro, and all the dependencies line up because they come out of the central repository. Either Maven has some hidden dependencies and doesn't like JDK 1.4 on XP, or they messed up with the tagging, or Maven just doesn't work as advertised.
Meanwhile, the problem with Maven is that it adds many, many layers of indirection on top of Ant. Although the output is pretty, and some of the reports are cool, unless things change soon, I'll be back in the Ant camp --- the 1.6 release of Ant promises to have a lot of the things I'm missing, like a rational way to reuse build files across a large project.