I would like to sidestep the Critical Mass issue, pro or con, for a moment.

I've always wondered what it would be like to ride in one of these. It might be loads of fun. I'd get to meet kazillions of cyclists of various sorts. It would be an adventure just to find out what it's like. And if it ever turned out to be a bummer, I could turn off somewhere and head home!

(I will, someday, for the fun of it.)