Beating the first Cup opens up new modes, but they're mostly filler. You've got three Cups, each progressively harder than the last, a Story mode that's nothing more than races with brief intros as to why you're racing and a Time Trial mode that challenges you to record your personal best times for each track. It's a decent package, but we grew tired of it within a few hours. The fact that Nitro Kart lacks a multiplayer mode, a staple of kart racing games, means it won't occupy your time very long.
For a launch game, however, Vivendi succeeds in bringing an impressive looking and fun racing game to iPhone. If you desperately need a racer, you could do worse than Crash's latest speedster.