Office Suite 2010 works great using either Windows 7 Ultimate or Vista Ultimate. If your work uses EN x3 with Word, then it is highly recommended that you wait until Endnote fixes the compatibility issues with Word 2010. They might come out with a new EN x4 to be in alliance with Word 2010. Since Office Suite 2010 is still in Beta, there might be enough time for Endnote to fix the problem.
I had to uninstall Office Suite 2010 and re-install Office 2007 to continue using Endnote x3.