1. Not just the number of tracks, but the variety of tracks. There are around 10-12 beginner tracks (by my definition) which are a lot of fun to do with a low-powered car every once in awhile, about 10 more intermediate-ish tracks, and around 15 absolute punishers, basically all the full-length real tracks as well as some of the high-end original tracks, and the rally tracks are all incredibly brutal with the new rally physics.
2. A-spec points. Now, there are a few glitches and miscalculations, such as the Dodge Ram or the near impossible 20 point races, or the incredibly easy hundred pointers, but for the most part, the A-spec system is accurate. And it makes the game much more challenging. This is especially good for those that want a challenge but don't get any fun out of running licenses and time trials and stuff where you're all by yourself. Even if the AI is poor, it's nice to have some stronger cars to go after.