Latest Series of WotC products

[PnP Fan]

Okay, I'm as anxious about 4E as anyone else. After playing Saga edition of SW, I'm even a little excited.
So, has anyone actually purchased the hardcover 4E Previews that WotC has been cranking out for the last few months? And, if you have, why? I've made my opinion of these products plain on other threads, but I'm not so opinionated that I don't recognize that some of this material may have utility to other folks. If there is utility, I would like to know what it is.

[Reel On, Love]

People who bought Keep on the Shadowfell did so in part to get an early look at the (quickstart) rules, in part to get a feel for how the game plays (which, if they discover it's Not For Them, might save them money on later books), in part because it's an adventure they can reuse later. I didn't buy it, because I don't buy modules at all, but I played through it. It wasn't bad.

[PnP Fan]

Okay, I get that, I'm not much on modules myself, but I understand that product.
What about folks who've purchased the hardcover preview products?