The portfolio based approach that has been pioneered by companies like Troux and which is now part of the standard lexicon by which organizations discuss their enterprise information technology asset base is creating an incredible lens through which to understand the organization.
It is useful however to distinguish between optimizing your current portfolio and building processes and governance that help you sustain a healthy portfolio. For example application portfolio optimization (APO) which targets redundancy and other inefficiencies in the the existing portfolio does not fix the systemic problem. This portfolio approaches treat the NOW problem. It may save you millions an dit may get you a raise, but the benefits while real are for TODAY. They don't fix the governance and business process issues that got you into the situation you are in today. Doing that means remaking the decision making processes that got you where you are today. You need to understand the value landscape.