I felt the racing in this game was very smooth and had some very intuitive races like against airplanes and hot air balloons but i think this game would have been better with cinematic cutscenes and a bit of character development like maybe your person hooking up with the horizion girl but otherwise it was a good game.
I love everything about this game. The festival setting, the online multiplayer, the selection of cars.. it's a really fun game and definitely worth buying it instead of renting it, because you'll get tons of game play out of it, especially if you play the online modes.
I have been playing Forza since the first one on the Xbox. I was super excited that they were going to have a free roam and rally that you could use with their massive amount of cars and driving realism. Sadly though that isn't what they did. It has more of a Need For Speed feel which people like me who love Forza for its realism will be a disappointed in. They also don't have a huge collection of cars that is use to in the Forza series and they took out tuning. Then the rally portion I was looking for toward the most is a whole another DLC you have buy.
Obviously you're using Gamefly so you are renting the game but if you are a Forza Vet then I don't recommend buying it and sticking with Forza 4. If you never have played Forza this is a good place to start.