On forms at least, if you create a composite but do not associate a layout with it, none of the component widgets will appear within the composite.
If you are using a managed block on a form, but you do not set the text ("title") of the form to anything, the detail panel will not resize properly when the window is resized. The detail panel will remain a fixed size and a scrollbar will appear on the bottom.
Many types of changes (like changing the form text to fix the detail panel resizing problem, above) do not take full effect if you are relying upon hot code downloading in a debugging session. You have to exit the application and restart it.
