Some good things, some great things
I'll skip the rambling about the history of the game, how many cups of coffe the developers consumed creating it and all that nonsense and get straight to the important bits you want to know.
Is it any good?
Is it worth buying?
Having played a few racing games in the past, I'll go right ahead and claim it's one of the better out there. Compared to Gran Turismo 3 and 4 on the PlayStation 2 it's not lacking in any department. Oh, maybe in the number of cars, but I'd say they have all the bases covered. They even have a few Lamborghinis, Aston Martins and Ferraris and not just the same old garbage collection of Japanese rice rockets and boring old American musclecars, and that's a big plus in my book.
I liked the tracks, variety of things to do both online and offline and how you can tune your car in pretty much every way you want. The one thing I think they didn't do very well is the sound of the engines. Some of the engine sounds are very good stock, but as soon as you start tuning the cars to get whatever amout of horsepower you get out of them, it just sounds terrible. You can barely hear the turbo(s) spin or the whine of the supercharger. You can however hear the blow off valves, but they aren't nearly as POOOF or PFFFFFFFFF-y as they should have been. Someone might say the sound of the engines is a minor complaint, but I disagree. The sound of a 1000 HP <insert manufacturer and engine type> is extremely awesome, and it's sad that no game (to my knowledge) can reproduce this, yet. The day will come, I hope. Maybe it's not easy to get every car sound recorded multiple times and with different setups each time and so on, but what do I know. I'm no game developer. :p
All things considered it's a great game that anyone who's interested in cars or racing should own.