This is something I use for scripts that are called by other scripts. If there's a wrapper script that manages flow, for example, it's easier to put the target script in debug mode than to find out where it's being called and put the parameter there. With that in mind, it's much easier.
MM
Comment on Re: Re: dbg - put any script in debug mode
Based on painful experience I submit that a complex system of scripts that call other scripts is itself a serious problem. Instead I suggest moving functionality into modules, and making individual scripts wrappers around the appropriate module. Then your wrapper script can be built quite directly by loading a bunch of modules and making the right calls.
This makes consistent error handling tremendously easier, and with a single confess you can figure out exactly who called what where whenever you want.