Search Engine Guide Editor Jennifer Laycock wrote a recent article that stands as an excellent argument for using targeted landing pages:

"[Using targeted landing pages] could mean the difference between a 2% conversion rate and a 10% conversion rate. Study after study shows that the less clicks you place between your visitor and a purchase, the more likely they are to buy. So why would you make them dig through your site when you could deliver them right to what they are looking for?

I understand that many business owners want to force their users to look at all of their products in the hopes that they will be able to upsell or cross sell their buyers. This is why the milk and bread is in the very back of the grocery store. That makes sense for a retail chain, but remember this: on the web, your biggest competitor is a single click away. You simply cannot play the same games with your customers that you can in a retail outlet. If you force your customer to play hide and seek, they will most likely seek out someone that makes it easier for them."

I couldn't have said it better, Jennifer!