I've always been comfortable with the term "geek" and uncomfortable with "nerd," but know people who feel oppositely.
When I think of the term geek, I think of it in two types. First, favorably, someone who is unusually enthusiastic about a particular subject; e.g., a carpentry geek, a food geek, or a racing geek. Second, stereotypically, someone who is unusually enthusiastic about fantasy or sci-fi, and is willing to look past all of the implausible elements of their passion and meet a lacking presentation or premise halfway so they enjoy themselves. Neither says anything about the individual's social skills; the most well-spoken attractive person in the world might also have this enthusiasm or passion.
When I think of the term nerd, I think Revenge of the Nerds. Nerd, to me, says less about one's interests and more about their social ability; that they are socially awkward physically, conversationally, or both.
Someone might be a geek, nerd, or both, but when I hear "geek," it comes with little-to-no negative connotation, whereas "nerd" seems negative. Other takes?