When installing 2010 Beta 1 please read the readme file for the latest known issues with TFS.

Installing VS/VSTS on Windows 7 RC and Windows 2008 R2 RC - The client products include SQL 2008 Express.  Install does not work properly on Windows 7 & R2.  The installation will go OK but will result in an error message..  You must update it with SQL 2008 Express SP1.  The readme has more information on this.  You can also checkout this post: http://blogs.msdn.com/dstfs/archive/2009/05/15/installing-tfs-2010-on-windows-server-2008-r2-rc.aspx

Don't run initial TFS configuration from the MMC console - There is a bug in the TFS configuration logic that will cause TFS's configuration of Sharepoint to fail if you do.  You have two choices - 1) continue with configuration directly from the install wizard (by leaving the "launch configuration" checkbox checked or 2) launching configuration from the command line using "%programfiles%\Microsoft team foundation server 10.0\tools\tfsmgmt.exe" configure  You can read more in Buck's post here: http://blogs.msdn.com/buckh/archive/2009/05/18/tfs-2010-beta-1-don-t-run-initial-configuration-from-the-administration-console-mmc.aspx

Installing TFS on Windows 2008 R2 RC - This issue combines the first two in an interesting way.  Only Sharepoint SP2 will install on Windows 2008 R2.  However, the TFS Beta ships with an early Sharepoint build, so a straight forward install on R2 will fail.  You have two options: 1) Install Sharepoint first and then install TFS or 2) Stop after the install wizard and before the configure wizard and update the Sharepoint installer to the SP2 installer and then proceed with the configuration.  But wait, you say.  Didn't I just say that stopping after the install phase was bad?  Yes, I did.  If you choose this route, you will need to take option 2 above and run the config tool from the command line.  I will update this post with a link to specific instructions for this procedure as soon as I have one.