Para quem anda a desenvolver Smart Clients com UI complexas a equipa de P&P publicou o CAB, Smart Client - Composite UI Application Block. Vejo o CAB como um compositor de windows forms (estilo web parts para a Web) e com um conjunto de serviços e interfaces que permitem criar aplicações smart client modulares.

Smart Client - Composite UI Application Block
This page provides an overview of the Composite UI Application Block. This application block is a reusable, source code–based component based on the Microsoft .NET Framework 2.0. It provides proven practices to build complex smart client user interfaces based on well known design patterns such as the Composite pattern, in which simple user interface parts can be combined to create complex solutions, but at the same time allowing these parts to be independently developed, tested, and deployed.

Podem também ver um webcast onde este application block é demonstrado
MSDN Architecture Webcast: patterns & practices Live!: Composite UI Application Block Overview (Level 300)