To advance in the game, you need to spend serious cash. And I’m talking about SERIOUS cash. Like over $100.
Imagine winning $500 coins in “free mode” in a race and your next upgrade is $100.000 coins. And a “promotion package” costs $6 (real dollars) for $35.000 coins. So three packages needed for one upgrade. And you’re gonna need a lot of upgrades. Not in the first 10 races (hence the positive feedback here probably) but after that.
Graphics design is nice, game design is boring (played one track, played them all) and the in-game advertisement is not only annoying but a plain insult to the intelligence of the player.
So if you want to spend an afternoon in a combination of agony and boredness, dive right in. Or you can do something more entertaining, like staring at a blank wall (just as boring, but less annoying).