My guess is that before long Apple will 'switch' their campaign. There's always going to be competition, and we all know that it's hard to position the iMac right (I mean without having a 2.8 GHz processor and without setting it at 799$).
I think Apple's _other_ ads are far better. Print ads right now (I don't know if you get the same in the rest of the world, but in Switzerland) show the iPod taking up all of the page. Only a title is on top of it, translated to English: "Wishlist."
Another one, quite similar in message, shows a Canon digital camera on the left page with the words "If you get this for christmas..." and an iMac on the right with "You'll want to get this.".
Apple has products that have the perfect styling for ads with product photos. They look elegant and have a similar attraction to people like a nice car or watch.
I personally wonder what impact the Switch campaign has made. I don't doubt it has made one, I just think that Apple should focus more on the stylish products again (in the ads).
The Gateway will, in my opinion, take away other PC makers' sales rather than iMac sales.