Actually, back when I went from v13 to v14 it installed without informing me to uninstall v13. And though it went through the installation just fine I did get an error message upon launching it. I forget what the error was but I was able to fix it by uninstalling WF and then reinstalling.
Since then I've always removed the previous version. The uninstall doesn't take long and just don't nuke the profile(s) in the process and you're golden.