Doing stunts helps increase your nitro (as well as picking up the things in the race, of course). Anyway, this game should keep boredom away for a while.
It could be useful if the fish you've caught don't disappear if you leave the game and come back later, and it would be nice if there was information in the game on what the different hats do (I assume they do something). Maybe not having adding or withdrawing money from the bank resetting the interest timer would be good, too.