Forumgoer Quaz51, the same fellow who discovered that Halo 3 ran in 640p, has said that the recently released Gran Turismo 5 Prologue demo does not actually run in native 1080p, but runs at 1280x1080 in-game and then is cleverly upscaled to 1920x1080.
[blockquote2]GT5 Prologue demo is 1280x1080p (Yamauchi know than in car game the vertical resolution is the most important for the visibility) but with MSAA 2x now! It's a very good compromise. They also improved the display of grills and electric wires and aliasing problems (compare electric wires in GT-HD and in this demo, it's big gap), the texture filtering is very clean and the HDR lighting is awesome! All this in 60fps with 16 photorealistics cars, it's impressive![/blockquote2]
True 1080p or not -- the game is still running at an HD resolution, and looks impressive.
The Neverending Upscale Discussion [Beyond3D]