Lounge

now "nerd" on the other hand... has yet to achieve positive connotations...

My perception is that there has been a shift in usage from "nerd" to "geek" and that, in the process, negative connotations were put on the side. Something somewhat similar to what happened with terms like "gay" and "queer," or what some people are trying to do with "bright." With "geek," the process probably started 15 years ago, as technology-savvy people became more valued socially. "Geek culture" came to prominence during the Internet Bubble (ten years ago). I remember a Wired article which tried to argue that being a geek was adaptive and sexy. The Internet Bust hasn't tarnished the geek image. Nowadays, "geek culture" is very influential but probably less widespread than people assume it is.
Nerd and geek stereotypes are connected to one another but the shift in perception has accompanied major social changes. In both cases, a "brainy" character is definitional but the value of "intellectual orientation" has changed. In both cases, the stereotype mostly applies to male teenagers but geek age and gender are now being recontextualized (albeit slowly).
The stereotypical nerd wasn't popular, in school or with girls. The stereotypical geek may be socially awkward but is often endearing.
The character who would have been a "nerdy type" before, is now portrayed as someone whose unique abilities (say, with computers) can be extremely useful. A bit like a "whiz," but with some character depth.
We could probably list a number of geek characters in television shows, from Seymour Birkoff in the Nikita series (in which my cousin played a 68er Frenchman) to Zack Addy in Bones. Even Gil Grissom in CSI: Crime Scene Investigation can be described as a geek. (What's funny is that I rarely watch tv. But these characters are easy to spot.)
By extension of "computer geek," the term "geek" is now applied to different groups of people who are passionate (sometimes to the extent of obsession) and knowledgeable (sometimes to the encyclopedic degree) about a given subject. I call myself a coffee geek and a beer geek, but I usually see myself as an outsider to geek culture because I don't share their cultural references. The term "freak" (which shifted in connotation and denotation several times during the past thirty years) is sometimes used as the mildly negative version of "geek" as in "gadget freak."
I'm sure Urban Dictionary and Wikipedia have good explanations of this concept since they're pretty much "pwned" by geeks!

Of course no offense was taken by me or anyone else, I'm sure I had the image of the carnival geek burned into my brain when I was a kid and saw "Nightmare Alley" on the Early Show. I just checked imdb.com and they credit the movie (actually the book that the movie was based on) with introducing the term "geek" to the public.

Oh my goodness, you guys are cracking me up.  Who knew one little word would spark such a conversation! 

Geeks and Nerds are both doing very well in the US these days.

Geeks

http://www.geeksquad.com/

Nerds (and possibly Geeks)...and one of the funniest shows on TV

http://www.cbs.com/primetime/big_bang_theory/

Steve