The new functions clos:copy-standard-object and clos:replace-standard-object allow you to copy slot values from one CLOS instance into another (or make a new copy) very efficiently.
The new MOP generic function clos:compute-effective-method-function-from-classes is called by LispWorks to compute the effective method function when a generic function is called with required arguments of specified types.
LispWorks Release Notes and Installation Guide - 2 Mar 2015