Microsoft offered a sneak peak back in February, and as of Tuesday the public beta of WorldWide Telescope has been made available, according to a Press Release issued by Microsoft.
Google Sky isn't supposed to generate tons of revenue, so from a business perspective, it doesn't matter if there are competitors. Still, towards the end of this month, a little toe-stepping may take place as Microsoft releases its WorldWide Telescope.
Google hid an Easter egg so well it wasn't found until nearly Labor Day, in South Africa, where I'm not even sure if they have Labor Day. Doesn't matter, it's not really an Easter egg, either, it's a flight simulator tucked inside of the most recent release of Google Earth.