He always struck me as being kind of thick. Like Mary is (was?) perpetually a sweet girl from the 50's/60's, I always got the impression that Billy was stuck in Opie Taylor/Beaver Cleaver mode as the world moved past him. That's just my impression anyway.
To put it another way, Courtney seems to get smitten over the kind of guy you'd bring home to meet your parents, which seems an awfully boring kind of person to pair up with someone as stubborn and energetic as Courtney.
I dunno. One of my "things" is vivacious blond with an attitude hooks up with eccentric inventor...it's why I liked the first forty-ish issues of Birds of Prey and why I 'ship Penny/Sheldon.