In my admittedly limited experience (Windows 7 x64, ant, Android SDK) ant is terribly slow to build projects with multiple source library dependencies and throwing hardware at the problem doesn't speed it up that much.
For example, most open source library projects that you include in a project don't change from build to build, but ant dutifully recompiles them each time instead of caching the output until the files in that project are changed or I manually clean the build output.
Which will then lead down a path of a set of scripts/utilities on top of said system to standardize on a set of targets and deal with known issues. And suddenly we have reinvented another old tool, autotools. We'll probably find ourselves in their troubles soon enough.
In fact, the only thing the autotools don't do, that every current tool does, is download the dependencies. Which, is not surprising, since fast network connections are a relatively new thing.
And I'm actually not sure I care for the download of dependencies thing. It is nice at first, but quickly gets to people pushing another thing to download, instead of making do with what you have. This is plain embarrassing when the downloaded part offers practically nothing on top of what you had.
Make, when used properly, is still an pretty smart tool.