Lots of changes in the first revision of the industry rigid board design spec since it was introduced as a separate module in 1998.
IPC-2222A, Sectional Design Standard for Rigid Organic Printed Boards, is characterized by the addition of several tables intended to simplify design decisions, particularly when it comes to materials. New tables offer at-a-glance differences in dimensional stability, CTE, and material consistency, by laminate type.
PCB thickness tolerances, key in assessing potential bow and twist, have been clarified, as the measurement method has been standardized to include just laminate to laminate, with no coatings or platings included.
Another table aids the understanding of relative costs, but keep in mind that laminate pricing is subject to change.