I just took the Flash MX 2004 developer certification exam this morning and passed with an 82% grade. I'd say it was a fair mix of both ActionScript 1.0 and 2.0 questions as well as some questions on more obscure Flash related concepts and its implementation.
Haven't seen a lot of candidates from the old continent taking the new certification exam yet, would definitely encourage anyone working professionaly with Flash on a daily basis to go for it. It's well worth the effort!
[update] You can find more information, including the exam guidelines and sample questions here. The "Certified Flash MX 2004 developer study guide" is a good book to help prepare (though hands-on experience is probably the best way to learn).