I have played and I own all of the Forza games except for this one. I have played it and it is awful, if you want a game like cruising USA then you will enjoy this. I should just be clear, this not a normal forza game in that it looks awful and plays even worse. There is no "feel" to the cars and it just seems so generic for a racer. Your money would better be spent saving it for Forza 5.
This game is great! It combines the reality of free roam and the intense, hardcore of organized racing. The DLC is great and there are loads of cars, and also the Rally DLC is great if you enjoy "dirt and sideways racing".
If you enjoyed all of the Forza series,you will fall in love with this game!