The first episode of Penny Arcade Adventures: On The Rain-Slick Precipice of Darkness has been officially dated for May 21, 2008, coming to Xbox Live Arcade and Windows, Mac and Linux. Cost to you? $19.95 USD or 1600 Microsoft points.
As you recall, there's no PlayStation Network version because PSN doesn't support Torque, with which the game is built. Full fact sheet follows the jump.