I wear them for dress and for casual as well, with blue jeans even. These are light weight so you can wear them in hot weather. They do provide a little warmth, but not very much. They look sharp IMO and are well made.
I bought one light gray one and like it so much that I then order a brown one too. Love em - no regrets.
If you are inclined, do not hesitate buy one.
I am 6' 1" 190lbs. I sometimes wear XL's, but prefer just a Large size in this item. I don't have a beer belly and these vests in a large for my size, is perfect. You can tighten or loosen them with adjustible straps that they have on the lower back.