I am getting where I can't keep up with these CTPs. Anyhow, this version is getting closer and closer to beta. In fact, they now have go-live licenses now for Windows Communication Foundation and Windows Workflow Foundation (nothing for Windows Presentation Foundation yet unfortunately). The other key thing it adds is that the "Cider" XAML designer has now been integrated into Visual Studio. This is basically the same designer that will be using in Microsoft Sparkle so it should be a lot easier to do XAML applications.
As usual, you need to uninstall any previous versions first. This page has a link to everything that you need.
WinFX January CTP
Read the complete post at http://www.dotnettipoftheday.com/blog.aspx?id=240