What are the most exciting changes to the BCL in Whidbey and Why?

I am working on a user group talk regarding .NET in Whidbey.  I have a question for the general pool of .NET developers.  What do you see as the most exciting changes in the Base Class Libraries in Whidbey and Why?

I like the threadpool changes because I have an application has become threadpool starved under .NET 1.x.  What's your opinion?

Wally