I'm two chapters into this story and strangely enough, it appears to be an appropriate submission to HN. Petunia ends up marrying a scientist (not that he or she or all the relationships are perfect or even great), and a "rationalist!Harry enters the wizarding world armed with Enlightenment ideals and the experimental spirit".

And it's funny (ADDED: very funny). A few too many slightly long digressions on "rationality", but worth a look, I think.

The author is Eliezer Yudkowsky [http://yudkowsky.net/other/fiction], who has also written other interesting fiction like the one about baby-eating aliens (Three Worlds Collide).