The Middleware Company performed a massive study on IBM J2EE versus .NET in terms of developer productivity, manageability, reliability, and application performance. Get the report here.
I think this is exactly the type of research that technical decision makers have been asking for. We have already seen multiple reports indicating Microsoft's performance advantage over the competition, but there has been a lack of information backing claims of productivity benefits on the Microsoft platform. We read case studies that claim an increase in productivity using Visual Studio .NET, yet those studies do not provide information showing what led to that productivity increase. It is great to see provable numbers backed by a methodology that prove that developers are more productive on the Microsoft platform.