I'm in the the "it depends on the wedding" camp. For an evening wedding, it could be too informal IMO.

But like lph, I see some utility--even if it's limited--in having some dressier pieces in my wardrobe. I was mostly done with weddings before I married DH, but he's younger so I find myself having to go to more of them again. I recently purchased, this dress for an upcoming afternoon wedding in which DH is a groomsman (he'll be in a tux). While I don't intend to wear it to work, I do I expect to wear it multiple times to weddings and other events. Depending on the shoe and jewelry, I think I can dress it up or down and wear it most seasons (if paired with a sweater or wrap). I also have a black cocktail dress, too, that has served me well for evening weddings.