I always thought vests were dorky looking.
Last winter, though, I bought one for a safari trip to East Africa and I'm glad I did. In that environment -- standing and sitting in an open-topped van with a bunch of other people -- it worked great. All my photo gear (and sunscreen, bug repellent, water bottle, binoculars, candy bar, guide book) was immediately at hand, and I didn't have to worry about forgetting my camera bag when we stopped and got out.
The one I used was a cheapie,
with the "Humvee" brand name, and it worked fine.
Haven't used it much since that trip, though. Looks too dorky.