Hi there - all the books I've actually bought from Amazon (probably 50 ish) have made use of the whole screen that the Kindle permits - there is a tiny margin all the way around. And even with the free books I've had from Amazon and other websites have displayed with this format.
I'm not a big plastic fan but I had a glossy Sony Touch reader and it wasn't enjoyable for me mainly due to an inferior screen. However the new Sony's look like they've improved tremendously. The Kindle 3 looks smart though it's plastic and the cases which are out already and some on preorder look very cool.