I've been running an early adopter program for a couple months now for a bunch of changes that we're making to the CLR binder/loader in the CLR v3 timeframe. The changes are related to the binding model, versioning, servicing and an add-in model. Also, just to be clear, this isn't .NET Framework v3.0 (AKA WinFX). This is the one after that. Here is the blurb that I sent folks who I thought might be interested. Please @ mail me if you are interested in participating.

We have been busy designing some exciting new changes to the CLR loader/binder. We'd like to start collecting feedback from customers about our change early, in order to ensure that the final product is rock solid. The first phase of the program is to validate that our changes are useful and to understand the compatibility of these changes. In order to collect this information, we’d like you to run two tools on your system so that we can learn more about how you – actually the managed apps you use – use the loader and GAC. The one tool is a tool that collects very basic information about the GAC, while the second tool is actually an instrumented CLR which logs data about how the loader, binder and domains are used. The next phases involve running a prototype version of the CLR that includes the new changes, but we’ll get to that later, as it comes available.

There are also a couple legal documents to sign, specifically an MSFT NDA and a license. I'm happy to discuss those if you want to go to that stage.