The WCF Documentation Team has started to release biweekly (!) documentation updates. The updates are made available as a set of .CHM files.
Mind that these files do not integrate directly into Visual Studio as the WinFX Windows SDK files do. Since VS integration requires quite a bit of setup work, the VS integrated help files can only ship with the regular WinFX Windows SDK CTPs. Nevertheless, the feedback from all customers we asked told us loud and clear that we should ship the documentation in this form irrespective of this minor usability inconvenience and therefore we do.
If you have feedback on the documentation, please use the "Send comments about this topic to Microsoft" email links below each documentation entry to provide feedback. Due to the volume that our team receives, you might not always get an answer, but your input is most definitely read and considered.
You can download the first (April 15) Documentation CTP directly using this link (20MB).