When you asked "why not use a shell script" it reminded me why not, and I added another section to that post. Shell scripts swallow errors by default, and if you do the Right Thing with respect to errors the result is still horrible error handling. Build systems have to handle errors right.

This was probably a big part of my frustration with BuildIt. When I used zc.buildout it was also horrible, though I'm sure it's improved some (though whether it has improved *enough* is a separate issue).