I cleared the game in a single lunch hour, but I'm not disappointed. The game design easily surpasses anything I've ever played on my phone, and there's a bucket of replayability. Pink/purple/black coins to get, speed runs on rally to try, etc.
Giving the first 3 levels for free was a good move - the install is essentially a demo that is enough to let a customer decide if they want to front for the whole game.
I didn't have a problem paying, but I've read a lot of whining on twitter and other places. Younger gamers have an expectation that everything on mobile should be free, but kudos to Nintendo on having the balls to stay away from cheap pay2win tricks and stick to an old school pricing model.
I don't know if it's going to turn a profit, but I really hope so. This race to the bottom amongst mobile game devs is madness and has to stop.