Not really.
When I am sure enough that I want to shut down to hit Alt-F4, I may as well
hit the shutdown on the menu. It is the accidental slips of the mouse that
leave me with a sleeping computer that I don't like.
As for using Alt-F4 for closing Windows, that only works if everything else
is closed or minimized. Otherwise it just closes the current window. And
it is a very awkward keyboard combination. This is just one of the few
things about Vista that I think they really got wrong. Well, actually I
have a whole list of things but this is one of only a handful that I think
is significant.
Dale