I haven't been playing much for a while. I got way burnt out on it, trying to compete every day. I still enjoy it on occasion, but the icon badging that you can't remove got me to delete it from my iPhone. It was pretty annoying seeing the count get into the teens! For the occasional player, that badging is obnoxious. The devs says they are going to make the icon badging optional in the next update, though. I'll reinstall on my iPhone when that hits. I did leave the game on my iPad, so I can still play it - I don't mind the badging there as much for some reason.
I think they did a better job with this type of competition in their game MotoHeroz for WiiWare. Having multiple courses to compete on each day, and having different race types (there's try as many times as you want ones, but also one-shot courses where you can practice as much as you want, but only get one shot at the leaderboard), really helps keep it fun. But also perhaps because I haven't been trying to compete in that every day. That helps too.