I just rebuilt the home server and installed Windows Web Server 2008, SQL Server 2008 and Visual Studio Team System 2008 SP1. I also ran all windows updates. But I still couldn't do a schema compare against the 2008 database.
After installing (manually) GDR Release Candidate 1
This is a very good update. I recommend it. I have had no problems yet.
It "now supports comparing Projects, Databases or dbschema files in any combination. For example, Project to Project, which has not been possible until now. Object Type Filtering. Additional ignore filtering options."
When using schema compare to deploy tables from a 2005 database to 2008, pay attention to Database Options and definitions. You might also want to filter by "New" items only. That helped me quickly deploy a production database to my new test server.
If you use the ignore filtering options and use the target collation, that will also help move a schema over. Also pay particular attention to users and schemas. They can cause your update script to fail because 2005 does these things differently than 2008.