Count me in the DIMS crowd too, although I was under the impression it was called simulator sickness, because it happens in various non-gaming simulators too and it's not really "motion sickness," it's "lack of motion sickness."
One trend I've been noticing from reading various accounts is that even if one game gets a person ill, other games might not. For me, third person 3D games are usually fine, but the 3D GTA game make me ill, and while FPS are a sure trigger for me, I can handle Marathon, Halo, and Metroid Prime just fine.
I'd like to beat it, so I've been keeping track of various techniques as I hear about them. My current collection of "cures" includes; Dramamine, ginger, keep the screen size small/large, play with the lights on/off, play frequently in short bursts stopping before you get sick to build up your tolerance, play through the sickness, wear a rubber band on your wrist/anti-nausea bracelet, only play games with high frame rates, turn on/off headbob, increase mouse/controller speed, increase FOV, increase/decrease resolution, sit closer/further from the screen, and of course, play something that doesn't make you vomit.