Well there's an upcoming conference just for you, running in Chicago, IL on May 25th-26th:

The Mainframe Migration Conference 2005 is the event for senior executives in companies relying on the mainframe for their mission-critical applications. It will showcase mainframe customers who have either completed or are currently migrating workloads of the mainframe and onto the Windows server platform, and highlight the business reasons for the switch and their experiences during the process. In addition, the META Group will give a presentation covering the rationale for replacement of mainframe legacy applications with applications running on the Windows platform based upon their research.

http://www.realtime-productions.com/mmc/