With a little more effort, we got Xilinx DocNav up and running with RHEL6.3. This includes multi-tabbed browsing with Acrobat Reader when clicking multiple documents in DocNav.
If you haven't used DocNav, you should try it. Quick access to the latest versions of almost all Xilinx doc.
One insight here is that neither Red Hat or Xilinx can redistribute Acrobat, we're told. So we found and tried a blog post that makes it easy to do a clean install of Acrobat Reader from the Adobe repos.
The RHEL6.3 desktop is starting to be a nice place to code.