The Daihatsu also shows the worst shadow mapping on the outside of the car. When you're coming up behind another car when you're racing (they're all Daihatsus), you can see this odd flickering and moving on the back of the car in front of you.. it's the jaggy shadow map crawling on the back of the car, appears to be only a few pixels deep. It clears up as you get closer, but it's still very aliased. I think this is what some people are seeing as "jaggy mess", is in fact only extremely low-res shadow maps.
Considering how it seems more of a problem on that car than any other, I'm going to assume that's it's merely a sign of a work-in-progress, something that will be fixed up by the time Prologue, and GT5 proper, are released.
Interesting about the resolution. While I'm not surprised that it's not 1920 (given that GTHD was only 1440), I am a bit surprised that it's not at least 1440 itself. Although the MSAA does appear to alleviate this somewhat, as the game overall doesn't appear as jaggy as GTHD does. As nAo said up above, the HDR+AA issue that leaves some jaggies apparently untouched by the AA. It's something I fight with in CGI as well whenever there's a sharp contrast between light and dark from HDR illumination or reflection.