The Game Developer's Conference is, without a question, the best programmer's tradeshow going. There's no other show that touches it in terms of technical depth -- introductory-level lectures at the GDC are what other shows would label advanced, and advanced-level lectures are the GDC are generally only comprehensible by excellent programmers already working in that particular area. I've heard much more pragmatic and correct things about one of the few areas where I know a thing or two (AI) than I did at the last AAAI meeting I attended!
Some sartorial observations: although a cut above most programming trade shows most attendees are still wearing t-shirts and jeans (but, like me, a black t-shirt and clean jeans) but there's definitely more hair color and piercing than you get at, say, the PDC. There's one fellow sporting a shaved head and a black duster a la Neo; perhaps a fan-boy, perhaps one of the coders of the Burly Brawl. There are a few guys in full metrosexual bloom: I really enjoyed the contrast between one guy in a Euro-cut suit standing beside a more-than-usually shabby guy with a comb-over. I glanced at their badges -- the metrosexual had a show pass, the shlub was a speaker.
I was the founding Editor of Game Developer Magazine 11 years ago and we bought the GDC tradeshow almost immediately. It's a bittersweet memory for me, because the magazine was actually the idea of an intern, Sander Antoniades, who deserved better rewards: we couldn't give him a full-time editorial position right away, so he switched divisions, and then left the company.