Originally when these products were announced, they were not going to be included in MSDN and they were going to cost a few hundred bucks a seat. That's a bad time. Well luckily people complained and they decided to include them in MSDN Premium subscriptions. Unfortuantely that does mean if you have MSDN professional you are SOL. Any way, it is still good news because these are great tools to design .NET and WPF applications.
Soma's Post on Expression
Read the complete post at http://www.dotnettipoftheday.com/blog.aspx?id=345