I would go further and say its useful for everyone. I imagine I am more risk averse than most people on the forum but Im happy to use useful apps in devel and testing if I know that the risks are acceptable so I generally read through the relevent threads before installing such an application.

I trust the extras repository though and just install anything that looks interesting as I see it as being inherently low risk. I appreciate the quality control and would not like the borders between extras and testing/devel to become blurred.