The WinFx Runtime Components February CTP (including Avalon, Indigo, and Workflow) has been released here.
There are a number of breaking changes from the January CTP. Ed has a good overview of them here. These changes are predominantly a result of community feedback. Please keep the comments rolling as we head down the stretch towards shipping, and remember to use http://windowscommunication.net/ for access to our latest and greatest community information. Happy coding!