This is the first GT for the PSP, also, Sony and PD wanted to make the game portable in every way, which means they don't want you playing career mode for 4 hours on the PSP-3000, or (go), like you would on your home consoles, so they limited the career mode a lot and really built the game around an Arcade experience rather than a full fledge time consuming / space hogging career mode...... LOL they should have called it GT:minis.
Doing so also made the game smaller in size which helps when trying to download for the PSP-go. Remember ease of access, portability, and simple / quick / undedicated game play is the theme for the PSP from now on.
The aim for Sony was to make the PSP-go and GT more digestible for the "on the go consumer", quick and easy game play, and just straight up fun out the box. This approach will anger many GT hardcore fans and reviewers no doubt, but that don't mean the game is bad. PD really can't make a bad GT game, well, at least I cant see them doing that.
This will be one of those games where some reviewers see the purpose of the changes (see above) while other wont, but I expect every GT fan to love it. And I hope that none of you thought that Sony would release a full GT experience on the PSP when they have the real game (GT5) coming out by years end?