As a Beta Exam Test Taker, I really cannot say much about the content or format of the tests.  I just took my third beta exam (70-443).  I felt more comfortable in this exam thatn the other two that I took, but it took me a lot longer.  Time just flew by..... 

Difficulty - I would have to say that the exams bump it up a notch or two from the older style of exams.  There is a lot more "deep" thinking and consideration on each question.

Test Guides - There is a test guide on the microsoft site to give a thumbnail of what is covered.  I really can't comment on it more than that.

Want to get involved (and you have studied /used SQl Server 2005)????  Visit the PASS website at www.sqlpass.org to find out more.  I just found out that more seats were added to 70-443 and 70-444 exams.  You need to act quick as I think the test taking window closes very soon.  PASS will also feature soon a web presentation on the new certification tracks for SQL Server 2005.  Stay tuned!