I am trying to decide between:
OpenFeint - http://www.openfeint.com/developers
Agon - http://developer.agon-online.com
ScoreLoop - http://corporate.scoreloop.com/features
All of the websites look clean. I don't know how many users they have but ScoreLoop has some recognizable games using the service.
Have you tried any of these platforms? Which is best?
I haven't personally tried any of these but Cocos2d also has a high-score framework built in.
I have good experience with OpenFeint. The developers were responsive to all my questions and helped me work around a few limitations.
Open Feint has some of the most well known apps as cross-promotions. Open Feint has a nice Objective-C API, matching Cocoa Touch.
Agonn has not as many apps for cross promotion, but are growing fast. Agon uses a C based API.
I Have no personal experience of ScoreLoop. But I understand that it allows much better UI customization than the other, making it easier to make the leader boards an integrated part of your game.
I just started experimenting with ScoreLoop, and so far I really like it. Integrating it into my cocos2d based game was pretty straightforward (just following the Getting Started document). It looks like there's a lot of room for UI customization, but I haven't really had a chance to play with this yet.
As far as I understand it, one of the differences between ScoreLoop and similar services is that in ScoreLoop, challenges are a central concept. So if your game can use challenges (mine will), this might be a good choice. It doesn't support chat, though. If you want more social networking features, OpenFeint might be worth a look.