A Microsoft Expression developer can help you create rich, interactive web applications with a user-friendly interface. They can leverage the suite's tools, like Expression Web, Blend, Design, and Encoder, to design, develop, and manage websites and digital content. They understand the integration of Microsoft technologies like Silverlight, offering a sophisticated multimedia experience. Their expertise can ensure a visually appealing, highly functional, and smooth-running website or application, improving user engagement and satisfaction. Hiring such a developer can significantly enhance your web presence.