just a quick note on updating the game...

After you have purchased the game from the Japanese PSN store and downloaded it, you will still have to perform another update of the game that adds the online racing component.

I have no idea how large this download is, but it took me the same length of time to download (maybe a bit longer) than downloading the whole game.

While mine updated first time, there have been a large number of people complaining that the update fails for them at some point or will not load at all. The only answer is to keep trying I am afraid.

By sheer luck, I downloaded mine at about 5am Japanese time and I guess there was very few other people online at the same time.

The online portion of GT5 Prologue makes this cut down version of the game worth buying and even though you will be racing against mostly Japanese racers there has been very few games where there is any lag (delay/jumpiness) during the races.