Hey guysII on Friday moments after it's rellease I was able to set up a Japanese PS3 account and download GT5 Prologue. Only 1 course,Suzuka and 5 cars but there are 16 cars in the grid and cockpit view.The HD graphics are great.I will report in more detail when I am at a computer ,right now I am using thePS3 browser which is very slow without a keyboard.
Edit: Just went and bought a keyboard for the PS3 so I can type faster, anyway if any of you have a PS3 there are instructions here at GTP showing how to setup a Japanese PS3 account, takes about 40 minutes because everything is in Japanese but it's sure worth it to get any demos or games released in Japan but not in Europe and N.America
Anyway although small GT5 Prologue is quite nice, there's a few short moviie races in it that shows Daytona Speedway and Fuji, but the coolest thing is the in-cockpit view, you have a rear view and side mirror and the slightest wheel input moves your onscreen wheel. The 16 car grid is also great, you always start in 8th. place and it's only a 2 lap race for each of the few cars you have. There are several cars that are locked but I can't figure out how to unlock them (my Japanese is a bit rusty) The physics seem much more advanced then GT4, sort of like going from GT3 to GT4 and of course the HD quality is fantastic, also the engine notes are much refined.