It's a bit different - Apple had the advantage of being the first on the market. They could afford to take some time before shipping the devices. Everyone else has to play catchup now; the longer they wait, the stronger the iPad becomes.
Apple does however release most of their products shortly after they are announced (new ipad nano, apple tv, iphone4)
Apple does however release most of their products shortly after they are announced (new ipad nano, apple tv, iphone4)