SCons is a top notch build system. It's dependency approach is both modern and effective. Written in Python, it can be extended very easily. It can even be configured to use make's deprecated dependency resolution for people that can't leave the 80's.
Documentation is seriously deficient and disorganized, and scons runs much slower than make on our systems. If I had control over the project's SCM implementation, I would run away from scons.
There are no 4 star reviews.