GT5 wasnt ment to be relased yet. Sony forced the release for xmas to promote there 3D TV's. There was a full proper version of GT5 when prolog came out but it was in 720HD sony made them go back to the drawing boards and make it 1080!
THIS IS WHY IT TOOK SO LONG!!!!
All cars will be premium, there will be more tracks, you will be able to customise your menus how u like etc... The game is still is massive production! Do bear this in mind! Poloyphony Digital has explained this. Hense in 1 month we have had 5 Massive updateds already!
With the game in such early stages still i think its great, my PS3 hasnt turned off.. We will see how far GT5 has come the time Forza comes out but we all know the graphics will not be beaten! Even the pampered GT4 cars looks great!!
i.e the supra i have (u will have to excuse the disformed bumper farside i had a lil bump lol):
http://img819.imageshack.us/img819/5255/highspeedring3.jpg
And as for the premium cars (which all cars on the came will become)
http://img189.imageshack.us/img189/8453/nicejl.jpg
Says it all really.