show() vs. show_all()

[Hrvoje Niksic <hniksic srce hr>]

What is the difference between calling gtk_widget_show_all() on a say
top-level window, and using gtk_widget_show() on every widget
descending from the window?

I find that all the examples and documentation (including the
tutorial) use the latter method, while I've been using the former in
my new programs.  Is there a subtle difference between a string of
show()'s and a show_all()?  Or, is it just a matter that show_all()
wasn't always available?