With the release of Reactive Extensions RC1, we are now in the final stages of preparing for our first official release on the .NET Framework and Silverlight as well as our out-of-band release for Windows Phone. We have told you that documentation would be available with the official release and we are pleased to give you the first pre-release documentation for the Reactive Extensions.
Please take a look at both the conceptual docs and the reference docs. Read over them and give us feedback. I know the doc writers would love to hear from you about everything from sample scenarios to punctuation. Post your feedback here and we will update the docs (both before and after the official release).