Best practice: Presenting Game Center options in iPhone game?

I'm more than halfway through development of my first iPhone game and I'm开发者_JS百科 currently implementing Game Center features for devices that support it. I have successfully added leaderboard functionality, but have some questions on how to present the Game Center features to the user.

Should Game Center be on and active when the user first runs the app?

Or should Leaderboards and autosubmitting highscores be an option the user have to turn on?

Right now I only submit the score when the user gets a highscore to keep data transfers to a minimum. I just want to make sure the experience is as hassle-free as possible for both Game Center users and people who don't care about highscore/achievements.

I would love to hear from other developers how you chose to present these features!

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I'm personally activating the Game Center immediately. If the user has opted in by logging in through Game Center application (or another game), why bug him? Turning off Game Center system-wide is easy. I'm also submitting leaderboard scores, since that allows me to see how many players (or at least Game Center users) enjoy playing the game continuously.

I don't think majority of users that are logged into Game Center would actually want choice. For comparison, OpenFeint provides the choice, but I find that annoying.

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What about collecting all the data and only sending it when the users sends the application to the background or terminates it?

From my personal experience I like the Game Center Integration as intrusively as possible. A short notice while game boots and/or a small banner on the highscore table should avoid to much distraction away from your game experience.