The game is undeniably beautiful to look are but the car models are probably on a par with Forza 2 and PGR4, not really surpassing them as you might hope. There are also a few occasions where the jaggies creep in which, given the alleged complexity of the models, you'd expect not to see.
So, is GT5 Prologue worth your money? That depends. Yes, it's half the price of other games, and yes it's the only serious racer available on the PS3 for the foreseeable future. But on the downside it doesn’t ever feel really complete. The lack of progressive difficulty and the limited number of tracks means races can get a little monotonous.