Over the last one year, I've been "talking" a lot about the great things that are coming out in Office SharePoint Server if you are a CMS customer. Yesterday, we released some great guidance and tools on helping CMS customers move from CMS to Office SharePoint Server 2007.
Check out the resources here http://msdn.microsoft.com/office/server/moss/2007/migration/ under the Content Management Server section! It includes 4 whitepapers and a CMS assessment tool. Make sure you read the Assessing and Analyzing Your MCMS 2002 Application for Migration whitepaper before you use the tool!