Penny gets him, at least as much as anyone does. She not only understands that his spot is his spot, but can recite the reasons why, even without eidetic memory. She caters to his food preferences, and gives him rides to the comic book store with only minimal grumbling. She's not well educated, but she's wise and smart in other ways. Sheldon knows he is no expert in such matters, however, her physical appearance is such that most would consider her beautiful.
He has known her for less than a year, but Sheldon has already decided. She will be his.