I have installed the Contact Log ready-made app to investigate how the logging panel works.
However in order to do so, and this would apply in a lot of cases - not just the ready-made apps but your own app, you need to deploy it to a web server in order to test it since it uses passed parameters between the various view panels.
This makes it difficult for non-technical people to develop such apps.
A 'development' mode interface where the views do not need to be deployed in order to test them out would be handy especially since preview does not work in these scenarios.

Also a means by which to globally switch off authentication. In the Contact Log app, you have to go into several views to disable authentication, which developing, in order to preview the app.