I don't count DNF's, but then I also have the custom of bailing within 50 pages if I don't enjoy my read. Or in the case of nonfiction, if I'm neither being entertained nor informed. I have always gone by page count in my book diary because I read books of all sorts of lengths.

Edited to add: I used to compare book/page counts with people, but all it really proves is who has free time. There's no point.