Joystiq has taken a look at XBLA title Portal: Still Alive, and has said that the game is just "extra challenges with a disregard for story."
From the piece:
If your wish for Portal: Still Alive is extra challenges with a disregard for story than this Arcade release is exactly what you want as it controls as well as it ever has with an Xbox 360 controller. However, if the realization that the additional content will solely be based on gameplay with a complete disregard for an additional story then Still Alive may have you worried that the Portal train is making an unnecessary stop on Microsoft's Arcade.
Full thing through the link.
By Mike Bowden