The CM system I'm using "journals" every change it makes to the system, so if you later remove or change a file or script in your CM repository, it undoes the old change. This eliminates virtually all configuration drift, provided you aren't making changes by hand outside of the CM system (which you should never do anyways).

This system has been managing about 100 servers and several hundred desktops at a single site since 2009, so the approach does scale. It has some problems that declarative solutions like Puppet solve, but at the same time it solves problems that Puppet/Chef/others have.