There are some things to consider after updating your Domino server or client. I got one main issue with the XSP command manager that sometimes produces errors and the page loading will fail. One reason can be an incompatible ExtLib version you may have installed via OSGi - as I did. I always used the latest ExtLib from OpenNTF. Up to now the version there is names 9.0.0 so I just deactivated this feature in my updatesite and restart the server without that ExtLib so the default 9.0.1 will be used. I have now to remove it also in my clients.
Ok, this one goes out to my colleages and all users who use the wonderful "Domino Navigator".
I just updated one of my machines to 9.0.1 - very smooth installing. But please uninstall the prior version first.
But there is one "problem" with custom toolbar icons. The toolbars are still there and working but the icons won't show up. So you have to reinstall the toolbars again.
To my ULC folk: reinstall the Domino Navigator and eStones toolbars again and restart the client. Then the images will show up again.