In the early 80s pre-announcing details and price points of your new product could prove to be disastrous. Especially so when there was a delay in releasing said new product. Everybody knows that this is what happened to Adam Osborne (and as usual, everybody appears to be wrong) but at least the saying has stuck around.
In the world of software — in particular operating systems — the effect seems to be harder to gauge. Apple’s announcement and iPhone induced delay of Leopard (OS X 10.5) didn’t appear to dent their financial results. On the flip side, developers of third-party software are likely to have suffered. I know that I have personally held off purchasing several applications while waiting to see how Leopard addresses the situations in which they have proven to be valuable while using Tiger (OS X 10.4). In particular, the brilliantly useful utility Hazel and Power Manager.