I upgraded from 7 and made some changes to a global template being used in a top level project which uses the old template path ([shared]…) instead of the new path (SharedTemplates/…), and the changes aren’t reflected in the instances. If I change the template path to use the new path, then it’s fine. I have hundreds of global templates instantiated many times, so it’s unfeasible to update every single instance template path.
Another issue that’s been raised before that is still there is that you can’t double click on a template whose path uses the old path. I’m guessing that these issues are connected.
If you are doing it manually, be aware you can multi-select a whole bunch of the same templates and update all of their paths at once. How useful this is depends a lot on how your component tree is arranged. I’m guessing you could do the shift-right-click on window–>Copy XML, search and replace in an outside editor, and then shift-right-click–>Set XML for this too, but haven’t verified.