A unique game, but some things hold it back.
Want to create a famous actor? You can do that. Want to make your friend? You can do that, too. Create your dream car, if you want, or even create a race track of your own neighborhood. Your creativity will spark like never before while playing this game, and it's extremely fun to do.
The racing part itself is pretty fun, but after a while, the levels begin to feel like carbon copies of each other, except with different objects placed in different areas.
The achievements you need to accomplish in order to unlock more items are usually pretty fun, but some of them tend to get rather annoying.
The cutscenes, while they aren't terrible, they are ones that you will most likely want to skip past. They don't provide much fun or story.
Playing online matches gets stale after only a few matches unless you're playing with friends, but being able to see what other people have made will definitely keep you interested. You can upload your own creations, as well, and seeing people download your characters, carts, and tracks makes you feel like you've accomplished something.
Overall, the creation section is what makes this game fun, but even that gets a bit boring after a while. Be sure to take breaks so you don't use all your creativity on one thing :)