I have a hi viz vest. My commute is 3 miles on streets, 14 miles on bike path. I hate wearing hi viz so much that I wait until the end of the bike path to put it on, and I don't wear if at all if it's sunny out. I usually only wear it commuting or if I'm riding somewhere at night.
Baby steps I guess, a year ago I wouldn't have been caught dead in yellow anything. I've noticed a relationship between age and fashion concerns, the older I get the less I care about looking dorky.
As for trendiness, you may see more cyclists wearing it, but the percentage of 18 year olds who make fun of you for wearing it willl never change.