I have one of those heavily starched Armadillo concealment vests. Fun fact: with it being as starched as it is, it's actually slower than my favorite fleece Woolrich Elite vest (which sadly has been discontinued).
There is a line of thought among some IDPA shooters that the stiffer the vest, the better it moves away from the gun on the draw stroke, so you end up with these starched to hell vests like the Armadillo ones. The problem is that theory doesn't actually hold up - a heavily starched/stiff vest works great if your goal is to have a huge dramatic arm sweep to clear the vest. All the really great IDPA guys don't do that though, they use a much smaller movement to get to the gun, and generally speaking wear softer vests that allow more, for lack of a better word, flow of the garment.
Instead of hurling my concealment vest off the gun, I've really focused my IDPA draw on just drawing the gun with as little wasted movement in the "vest" area as possible. It works a lot better with a pliable vest like the fleece Woolrich than it does with a starchmonster.