David Abrahams wrote:

... chosen Scons over Boost.Build. It would be useful for us to understand some of the reasons why, if some of you wouldn't mind letting us know.

At the point of the decision against bbs times ago the poor documentation and the unclear state of usability of bbsv2 were reasons against bbs. Using an existing powerfull language as base for a build system is unbeatable concerning expressiveness and extensibility: You can hack and extend SCons in any way with ease to get what you want. A litle bad aftertaste was and is that SCons still performs poorly in real-word projects. 0.02 $