I never noticed this page until right now... it is interesting that they put the bottom of the page as a "hot" location, and I agree, I use banners on that spot and get good clicks because once the visitor has finished reading your page's content they can click on any ad they find interesting. http://www.google.com/adsense/tips
Yes, and I have found it quite useful. Another thing I have noticed is that they ecourage some things that others here have labled "shady". For instance making the ads/text blend into a page. Done right, it looks good, and assuming you have a real content rich site, they do their job for the advertisers IMHO.
Blending the ads isn't shady, but hiding them completely and putting all kind of images to try to hide them even more like many people try to do is what seems to be shady...
They launched this page shortly after they mailed out those little green tips booklets to publishers quite a while ago. The heatmap was added to the page back in April (although those publishers who went to the AdSense Bay Area Forum got an advance copy of it then).