Should you answer back to their ad?

Last week, I wrote about not letting your competitors’ actions lure you off your path.  (There were some really smart comments, so check them out.) 

And then, lo and behold…an excellent example for us to discuss appeared.  Everyone is familiar with the brilliant Apple campaign Mac versus PC.  Just in case you’re not…here’s an example.

And now, Microsoft has come out with a TV spot that answers the Apple campaign.  (Sorry for the quality, it’s the best I could find.)

Good idea or bad?  Do they sound defensive?  Look reactive?  Do they do a good job of making their point? Do they change your perceptions?  Would this influence your buying decision?