John, take a look at com.google.gwt.sample.expenses.client.SlidingPanel. In particular, note its implementation of HasOneWidget, which makes it friendly to ActivityManager.
Also note its implementation of HasWidgets, and its use in ExpensesShell.ui.xml. You're able to set the thing up in a ui.xml file, and then call setWidget() to transition between its children. It winds up being pretty nice to use. I haven't looked at this patch yet, but can it do these tricks as well? http://gwt-code-reviews.appspot.com/1340803/show -- http://groups.google.com/group/Google-Web-Toolkit-Contributors
