Looks like there is going to be some good sessions at the PDC about Yukon. I think Roger's session about the Yukon Service Broker sounds the most interesting:
The Service Broker is a new feature for "Yukon" that incorporates asynchronous queuing and guaranteed messaging into the SQL Engine. This provides a whole new way of writing highly scalable, highly reliable database applications. Learn what the Service Broker is and the unique advantages the queuing and messaging built into the database offers.