It's a lot more fun having 16 cars on the track, but it's what I expected. At the beginning of the race, I sometimes crash or wait for all the cars to go by. Then, I have fun passing by all of them and coming in first before my two laps are over.
Though, the AI is not perfect, and it's far from it, it is improved. However, they still bump you off the road, once in a while, especially if you 'suddenly' get in their way or take the same path they do. I did notice some cars tend to get out of your way more than others. The Mustang never gets out of your way and is the most difficult, all be it, fun to overtake. It's a challenge compared to the other cars.
I hate using the controller, though. The cars still 'twitch' too much when you steer them around. I hate that, but what can you do about it?
Don't worry, you'll love the game. It's a lot of fun! Better than GT4? Maybe, but I need to play the full version to see if that's the case. The only problems I have with it are the graphics, which can look bad to fantastic, and the sounds which are better than GT4, but not by much, IMO.
Oh, I got punted into the grass once, and the revs where high until I got back on the track. But, I believe GT4 is the same way. No other rev spikes, that I can recall.