Project Gotham Racing 3 is what I would call a "technical" racer, or a "driving simulation". The handling of the car, the stickiness to the course, weight distribution, braking and tire behavior, and more... all modeled as closely as possible to the real world. You don't hit 90 degree corners at 100 miles an hour like in an "arcade" racer. Try it, and you're gonna hose yourself.
I'm personally not a big fan of this kind of game. I want fast-paced action rather than knowing that the driving faithfully matches reality. I don't need reality. I want adrenaline. I want to smash through traffic, slide around a corner, hit my nitrous, and leave competitors inhaling my exhaust.
But! This game is a teriffic challenge. You have to be on your game. If you miss that line through the corner, then you're out. Hit a wall? Cut too sharp? Bash into another car? Don't do it. You have to draft, take the lines tight, glide thru your opponents... all necessary parts to winning the race.
Meanwhile, there is a "kudos" system scoring you for good driving. Do all the driving right, and you get big kudos bonuses. The kudos then bring on some excellent unlocks and other goods.
And the game is *beautiful* ... it really showed off the graphics of the 360 at launch time. As you fly by the buildings and crowds... all detailed. The cars are kick-ass modeled. Sound is awesome.
This game is very much recommended if you like simulations and "true" driving. It is the best out there for that sub-genre of racing.