Reading between the lines it seems the cars, driving, etc. is all fine its the lack of a career or guiding gameplay device that's the issue.
I wonder why they left it out? Can't have been space, surely? Did PD think that on handheld people would just want to chose a car a track and drive in short bursts? I can't think of any reason not to have it given what is included with the game - it can't be for a technical reason, reading both reviews it seems for the most part they did a good job getting the title on PSP technically.
Mind you, I find the idea of a driving game on a handheld rather perplexing anyway, so what do I know...
Try to be reasonable... its easier than you think...