How Open Should You Be About Upcoming Product/ Service Announcements?

Earlier today, Apple did something they almost never do. They issued a press release about their upcoming cloud services offering, called iCloud (0 points for creative name, 2 points for consistent product naming) that will be announced next week at their annual Worldwide Developers Conference (WWDC).
Historically Apple has always been a very closed company, they have pulled out of all external trade shows such as CES, moving to using their own Apple events to launch new products/ services. They have pretty much zero presence on any social media site or service and often ignore any complaints by users. ¬†After having four Apple Mac Book Pro replaced I’m convinced that they don’t care or worry about customer service.

So we turn back to you, the PR In Canada community – how open should you be about upcoming product/ service announcements? ¬†Anyone have any examples of success you’ve had with pre-announcing product or service announcements?