I've heard it both ways, which one is the term for the cooler kind of person. And I lean towards the opposite of your interpretation. To me, "geek" is always negative, where "nerd" can be either way, negative in the eyes of jock-types but affectionate among fellow nerds (who are smart but awkward).

"Geek" also creates an image in my mind, a negative one, probably based on hearing Fred Blassie's song "Pencil Neck Geek" at an early age. Nerds seem more physically varied in my mind when I picture them (ranging from Comic Book Guy on The Simpsons to extremely hot Willow on Buffy the Vampire Slayer.