Not sure about the release date (rumored to be late December), but there seems to be some interesting features:
Videos:
http://news.vgchartz.com/news.php?id=4867
Features:
Polyphony Digital have revealed some awesome new features for Gran Turismo 5. 1000 cars, Youtube replay output, PS Eye feature... much more inside
* 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)






