Outside of LAN parties (yeah, I'm one of those nerds), Gencon is the only major convention I've ever been to. We do have a local Comic con that i attend but to put that in the same class with Gencon, SDCC or PAX is a bit like comparing a snot-nosed tee-ball player to Mark McGuire. This was our third of fourth year attending and it was easily the best year we've experienced. If you enjoy games of any sort or just splashing around in a sea of nerd-dom, I recommend you check it out at least for a day.
We had the fortune of experiencing all four days this year and as long as our wives will allow it we'll make that a tradition. We also got to stay downtown this year. I think this was key in our enjoyment. There is really nothing more deflating than packing all your stuff up to get back in the car and drive to some shit-hole motel on the outskirts of town at the end of each day. Staying on location gave us easy access to bathrooms that weren't also science experiments and we were able to enjoy a bit of the night life as well. Definitely worth it if you can pull it off.
We did not experience the scene depicted in today's comic but don't think for a second that it didn't play out time and again throughout the weekend. I've done the math and consuming cosplay is 23.6% of the fun at Gencon. Just don't try and game while Leeloo is at the table.