•  Models included
  1,000 vehicles
  170 Premium new models (full interior modeling, the interior corresponds to vehicle damage)
  830 kinds of standard model (some are from Gran Turismo 4 that have been carried over to GT5)
• Courses
  60 courses confirmed with 20 or more to be revealed
• Physical simulation of vehicles
  Physics system simulation is brand new
  Represented is full fall in vehicles [possibly rollover]
  Damage representation (reproduced in full by real-time collision deformation)
  faithfully reproducing the behavior of electric cars, i.e. Prius, Insight, hybrid cars and the latest Tesla model
• Arcade Mode
  Single Race
  2 player battle
• GT Mode
  World Map
  My Garage
  Car Dealer
  Tuning Shop (parts, tires)
  Car Washes/Oil Change
  Race Championship (Series system, point system)
  License Test
• Online
  Open Lobby
  Text / Voice Chat
  Private rooms
  Online Photo Album
  Online Replay Album
  YouTube replay output
• Photo Mode
  Photo Drive (Circuit)
  Photo stage (Stage Photo mode only)
• Gran Turismo TV
  Video output to a PSP or PSP Go®
  Progressive Download
  Improved
  user interface
  Continuous Play for videos
• Museums
  The Gran Turismo 5 Prologue version
  More information at TGS
• Sound
  Custom soundtracks (Use songs from your PS3 hard-drive)
  Dolby Digital 5.1 and 7.1
• User Interface from Gran Turismo 5 Prologue, and the same design concept.
  The icons change color
• Able to track the movement of Cockpit Camera interface (confirmed in full 3-D. The camera can be fully manipulated and you can opt to have your head tracked by the PSEye)

This sounds very promising for Gran Turismo 5.

1000 cars is amazing variety, and is sure to please everybody who gets to play the game.

PS Eye functions though, is something very new.
Possibly having your head movements tracked by the camera while racing, for an even more realistic experience?

Taken from GTPlanet