We've been working with the release candidate for a while - the official release has recently been posted - download from

http://www.microsoft.com/downloads/details.aspx?FamilyId=6C8911C3-C495-4A03-96DF-9731C37AA6D7&displaylang=en 

I've also been working a bit with MP Studio Lite (fre edition) from Silect Software.  It is a pretty slick tool that is a good companion to the authoring console.  Take a look at

http://rorymccaw.spaces.live.com/Blog/cns!2C4CD58BB2826E21!3139.entry