It is unusual to have two "waves" of pre-release product out at the same time, and that is what we have with Whidbey/Yukon and Longhorn/Avalon. I take this as a sign of the depth and breadth with which transparency and early customer feedback are being widely adopted within Microsoft. We're getting more customer feedback, earlier in the product cycle, and in a more targeted way.
The VS 2005 CTP's are a good example, as is the new product feedback system that helps us more efficiently close the loop with customers. Whidbey's inclusion of the small and quick-installing Express SKU's helps drive feedback earlier in the cycle as well. These SKU's reduce the cost of early adopters trying out the product when they only have a brief amount of time. Since early adopters will install and uninstall multiple times (in some cases many times) before release, this can be a big time saver. Even with my limited knowledge of economics, I can tell you that driving down early adopter costs will drive up early adopter usage and feedback. Economics theory is probably neutral on this point, but I'll make the leap -- that can only lead to better and better products for C# customers.
Happy C# Coding!