I've only seen a couple people on the site here who are in the area. I think you, tazzel, and myself are the only active people on the forum in the Denver-ish area.
I know from riding around that there are other spyders out there, just haven't met their riders (always see them in motion, never stopped anywhere). I tend to gauge the bikes by color, since no one seems to own a duplicate color around here. In the Boulder to Firestone area, there are: a red one, a black one, a silver one, a white one, and a yellow one. There may be two yellow ones though, I saw a guy wearing gear one day and not the next who may have been the same rider. Unfortunately, I always see them when I'm not able to try to talk to them. They're always going the opposite way, or I see them from my office window in Boulder as they go down the road.
With all the cargo space these things have, it would be fun to load them all up with some food/drinks and a little mini gas grill and go for a ride to someplace scenic for a picnic.