They're really going to have to stock 3DS demo's in as many places as possible... every retail game store possible, naturally, but also booths, etc.
Also, I think word of mouth is actually a lot better a form of advertising than many people realise... while adverts are certainly affective, they still lack the intimacy, and you might be inclined to believe that the product might not be as good as you believe.
If you hear about a product from a friend who gives it high praise, however, your far more likely to buy it.
With all these journalists giving it high praise, I think that will help it sell more than anything really. glowing 3rd party opinions, if advertised, can give a very powerful message - "this product is awesome and other people agree with us too!"