Until then, the release notes can be found here: http://technet.microsoft.com/en-us/library/ff977012.aspx
Main things to note is it advises downloading the latest help file for SCCM as it's not updated during install, but the link provided relates to the March 2010 updated help file which does not contain any of the R3 information.
However, the help file is up-to-date on the Media until they fix the link.
Also, don't forget that all the new Power Management reports in R3 require SQL Reporting Services, so if you haven't got it installed and working yet, time to get it ready!
As Marnix Wolfe is a fan of the saying.. RTFM, RTFM, RTFM!
I've already started to notice a few bits in the documentation, the main thing being the need to deploy the hotfix mentioned in Article 977384. Fine, except this article doesn't seem to actually exist. I'm
Angie Stahl however does have a really good blog post about using SCUP to send this update out.