What was formerly known as Feature Preview 2008 just now has been released: the XP embedded Update Rollup 1.0.
This link leads to the eval edition. If You are an OEM, please acquire the bits via the OEM page.
The Rollup includes a lot of service patches for XPe FP2007 as well as .NET Framework 3.0.
Please be aware to uninstall the Feature Preview 2008 as well as the QFE components that came with them before installing the final version! There is a help file included telling You how to do this.