I'm currently chasing a wild goose of an idea in Drupal 7, and found myself in a situation where it would be really convenient to run the Drupal install script through a debugger.
Most of the clients I set up Drupal web sites for are not experts at hand-editing HTML, and prefer to use a WYSIWYG (What You See Is What You Get) or Rich Text editor to create their content.
A few months ago I set up Varnish on my Macbook Pro and have deployed it for a production site which serves anonymous and (a lot of) authenticated users.