I'm h1 for main title guy. And main title is decorated site name, or as you call it, logo. Here's the point -- in header of website, logo is not actually a logo, it's illustrated site's header. Designers just like to design it as logo.
What's wrong with LOGO -> H1?
Google
About Us
Now, as h1 is the most important section as it tells visitor what's it all about, the visitor cannot understand the page, because h1 is too specific. About who?
Google
About Us
This page is about Google. Here's the section about us. See -- there's no question? All is clear.
Second point.
Page structure. If you put site main heading into div or p, there's nothing to associate it with.
Google
About us
How can i associate About Us with Google if h1 comes after? Because all that comes AFTER H1 is associated with it, not what becomes before.
Google
About Us
About us belongs to Google. No questions.
Third point.
HTML is language to DESCRIBE information. Therefore you don't display information, you describe it. And each page is independent. Therefore you describe one page because there are no associations between pages. Just links that link individual pages.
Google
About us
THIS page is About us. Who/what it is? Unclear. It just describes something called "About us".
Google
About Us
This site describes google. And there is a section About us. Us = most probably google, cause the structure describes it that way.
I hope I made my point :)
Villu
PS! You cannot use h2 - h1 - h3 as it is illogical, therefore a big fail. Just because w3c haven't said it is not allowed, doesn't make it valid. It's illogical, think about it.