The game is bigger. Or at least less organized. More cars, more tracks, all good. A huge map you have to navigate around to do much of anything... Not quite as good. Still, you get used to it fairly quickly, so it's not a big deal, really.
The first thing you need, of course, is a car. You start out with 10k credits, which seems horribly inadequate until you realize that GT4 added used cars. So, I got myself a black '98 Honda Civic hatchback (it wouldn't have anything to do with the fact that my first and only car is a black '98 Honda Civic hatchback, not at all, nor could that possibly explain why I started with a black Honda Civic hatchback in GT3, either. But never mind that). Of course, the only color the '98 Honda Civic is available in at the beginning of the game is white, so I spent a few weeks getting my B and A licenses (it updates the used cars every week of game time), until one was available in the right year and color. (I also grabbed 100k credits from my saved GT3 game and upgraded it right quick, but never mind that, either).
So, how does GT4 compare to GT3? It's better. Much better.
First, racing... The physics seems noticably improved. Cars don't seem "heavier," exactly, than GT3, but they seem just a little bit more... "There." Going around curves at the edge of control feels like... You're at the edge of control. The AI is better, too. Or more "real," at any rate. The other drivers seem a little more "random," i.e., they don't always do the exact same thing when in a bunch, and they make mistakes.
Of course, there are more cars. A lot more cars. Old cars. Lots of old cars. (I'm going to get me a '69 Corvette Stingray. I can't buy the '65 Mustang, though, looks like I'll have to win that one, darn it.) New cars. Weird cars. Very weird cars. Jay Leno's tank car (woo!) The scary old three-wheeled Diahatsu thing that belongs in a third-world country. The Model T. And my black '98 Honda Civic hatchback.
And tracks, ranging from a parking lot (where you can go knock down pylons or whatever) to the Grand Canyon. Oh, yes. All of them look better than GT3, including the ones that were in GT3. And the new ones... The standouts are the Grand Canyon, New York (which goes through Manhattan and Times Square), El Capitan (which winds through Yosemite Valley), and my favorite, Hong Kong. There's also the Nuerburgring Nordschliefe, which is a monster, difficult and long at almost 13 miles (!). (There's graffiti all over that track -- I suspect it's quite authentic.) There's even a drag strip... Down the Las Vegas Strip.
The game is beautiful, from the updated car graphics, to the much more realistic looking spectators that occasionally jump out and take your picture before rushing off the track as you approach, to the updated look-and-feel of the interface, which generally looks much slicker than GT3. The sound is upgraded too, with the wind whistling by at high speeds, and much more tire noise. If you drive like me, it's a veritable tire symphony.
For all that, it's pretty much the same game as GT3 at its core, but upgraded. There are a few truly new things, like B-spec mode (where you "coach" the car instead of driving), but I haven't tried those yet. I don't know when I will; I was already addicted to the original GT3, after all, without all this newfangled stuff. I did fool around with taking pictures of my car a bit (if I could somehow get the pictures off the playstation and onto another computer, that would be a lot more interesting. Oh well).
But yes, this game will be sucking up all my free time for a while. It was worth the wait.