The Career mode sees the biggest changes, and quite rightly too, considering how crap it was in Juiced. The calendar system - whereby you painstakingly picked out free races - is gone, as is shelling out more cash on repairs at the end of every race. This system quickly saw you enter a downward spiral of having no money and being forced to flip through the calendar until the next free race showed up. It won't be missed.
Now, you start in the rookie league and must work your way up from here through leagues seven to one before the going really gets tough in the World Class and final HIN Elite group. Each league contains several challenges and a promotional event that unlocks once you beat a few of these challenges. Complete the promotional event and you move up to the next league. It's simple, no-nonsense and ensures you always have a choice of events to try, no matter how bad you are.
In the lower leagues, there'll be simple objectives such as "place third or above in a US circuit race" and "break the speed barrier of 180mph," but by the time you reach league four you'll be required to complete more difficult tasks like "win a $35,000 driver bet at a Drift event" and "score 1.5 million points in a drift endurance," which means performing one continuous drift without hitting a barrier. Easier said than done.