GreatLemur (echoing others) said:
Man, I ain't paying for advertising.
If you look at these as a big advertisement that you pay for, you're absolutely right to avoid them. But I don't think that's really what they are.
The development of 3rd edition and Eberron both generated hundreds of pieces of concept artwork that never saw (or were ever intended for) publication. The same is true, I'm sure, for 4E (we've seen a few bits and bobs). I think it's brilliant that they're opening that up to us, and access to that alone is worth the price of admission to me.
I expect the writing to include candid "behind the curtain" type stuff about why they went in the directions they did; the sort of thing that's normally only available to a few score attendees of Gen Con designer panels. I welcome the chance to get a glimpse into the designers' intent and see what drove their philosophy.
Most importantly, as a D&D player, I like to go into the game shop every month or so and pick up something that will inspire my gaming life. Usually, that's a D&D supplement, but frankly, I don't really want another 3.5 book at this point, now that my 3E gaming is winding down toward its conclusion. What do I want? Something that will inspire my thinking about the game I'll be playing next Spring. These books sure look like they'll fit the bill.
So YMMV, but I don't look at these as "advertisements" at all. I think they'll be filled with content that's every bit as good a value as most of my D&D purchases--maybe more than some!