Using ensure in yielding methods

I never really ever find too many occasion to use 'ensure'. It's a Ruby keyword that you can use for blocks of code that ensures, no matter what happens, exceptions or not, the code will be run when the block is finished. And then a quickie that I found in the rails core:

  def silence_warnings
    old_verbose, $VERBOSE = $VERBOSE, nil
    yield
  ensure
    $VERBOSE = old_verbose
  end

It does something simple, just silences the warnings for a particular block of code. On first glance, I would have just written it without the 'ensure'. However, that won't work for yielded blocks that call return or if exceptions are thrown in it, I think. This way, no matter what happens in the block, it will always restore the state that it changed.