My thoughts:
Sound:
The Ferraris are whinier, the S7Rs are louder, and the sound is just better. The engines are amazing, and hearing them on an idle stop just gives you an idea of about what you're going to push. The crowd is a huge improvement. Hearing the whistles and the horns is new to me, and adds to the realism.
My negatives are hearing the pit sounds when you're out across the track watching the cars race. 1 more is not hearing the nuts being taken off the wheels (though you still hear the tires hit the road).
Cars:
The improvement is way better. The cockpits are much nicer. The headlights are greatly improved. They're much more realistic. You can clearly see the lights in the dark, and tell which car is which. Not to mention, some of the cars like the Viper look like a freaking badass beast at night in your rear view mirror. The same pretty much goes for the brake lights. Much clearer, and much nicer to look at it. The cars are much cleaner, much more graphical, and again, nicer to look it. The cars' drivers are more realism, and while the shifter doesn't move, who cares? At least it's there, and it looks nicer. 1 other deal, I personally like, is that the Murcielago is finally a competitive car, and can now run with the Saleens and Ferraris.
Negatives: Minor nitpicking that they don't move (but who cares again). Another minor is the driver's changing in the car, but their hand not when you're looking at it outside the car.
AI: Real big improvement here. Much more realistic in racing, and now, your 2nd driver is actually GOOD. He finally has the ability to set some good lap times and be competitive in the race.
Graphics:
Ok, you can EASILY tell its improved here. The brake heat is now here, the lights are better. The scenery for the track is greater, and as said, the cars are obvious. There really is no negative here.
Other:
Pit crews are a perfect addition. The animations aren't perfect, but their there and they, like other things, add to realism. Sadly, I can not say about other cars though there appears to be an option for them to have visible ones. I say this because, well, on a 15 lap race, they don't pit.
Options are a very noticeable thing, and they were just what I wanted. In the past, I've said I've liked to let the AI race, but I can never watch my car finish the race.
Not the case here.
Here, you have 2 options for AI.
1) Either you or your AI start the race. Now, when he pits (given you chose him; and he actually does pit, whoppee!), you had another option. Either you or him stays in the car. I chose him, and sure enough, you're just asked what you want done with the clipboard as usual. Sure enough, he pits, gets it done, and goes out racing.
Now, when he is chosen, and on Qualifying or Practice, he does something similar to Sportscar GT. If you remember this game, when you switch to your 2nd driver (a 30 second change). So, afterwards, when he left the pits was his decision. In GTR2, you have the choice to wait him out, OR make his ass go. In the 1st, after 1 time, I remember he couldn't go twice. I can not say for this one since he never pitted.
Night time racing as an option. This is definately a much wanted one for some of us. Though you can't choose it for Qualifying and Practice, you can choose what time you want to race. Set it 20:00, and you're racing at night. This is a pleasure given GTR never let us experienced any courses at night besides, what, 2? Spa and the oval, correct? Not the case here. Now it'll appear we can race Monza, Bahrain, and any of the other courses when we want. The night time racing is simply cool. Racing in cockpit view, the changing of the lights to a darkness is great and gives a feel of realism as you try to see your wheel. In the dark spots, you have to judge purely on headlights and brake lights. Once you reach a lightened area, it gets easier, and it looks great since unlike some games, the whole area isn't lightened up by 3 lights. The "color" of the lights is also more realistic. The lights in pitland form a more realistic shape on the road, esp. over your pit area.
Time or Laps is another nifty little feature in the game. If you only 45 minutes free, set your time to 30 minutes. Or if you feel like doing a 10-lap race, we now have that option.
The weather seems different and more based upon rain than other effects like fog. This is still an neat little improvement to see during the race.
Damage: Still a bit the same, and still a little strange. Slight taps still cause some wierd damage, such as either too much, or none at all. Still, enough to be satisfactory.
Handling: 50/50 depending on your likeness. For those who want hardcore, no hold's bar from the 1st, may find that even at a Pro Level (Still very hard), the car's are a little easier. However, the other 50 should come as a thanks now that more people can drive in the game.
My negatives are very minor because, well, these are small things that are good enough.Either way, it'll be a definite buy from me, and I can't wait to give me a run on GTR2's 24 Hour races.