This article from Rob Maher focuses on how to increase productivity. It discusses how changing a project staffing model could increase the productivity of project teams (PDF document). There is published evidence that short-lived groups of people brought together for a project are correlated with lower productivity. His view is that in an agile world, teams are permanent and the organization optimizes at the team level. Permanent teams enable consistent estimation, which is not possible using the matrix approach.
Permanent teams work on one project at a time, starting a new project from queue when they are finished. There are fewer active projects running concurrently which is a cause for slow delivery. His conclusion is that “moving from a matrix system where project teams are formed ad-hoc to a permanent team structure – changes the nature of the way projects are executed and can significantly increase productivity of teams. A new approach can help with estimates, eliminate unnecessary resource management and meet the increased throughput demands of the organization”.