TUAW has published an interesting interview with OpenFeint's founder Jason Citron here, where he talks about the future of the platform and the Game Center announcement.
From the post:
"So why now? "Apple stumbled onto this," he told us. "They were trying to make cool phones, an iPod and a phone coming together. They opened up the SDK, and all of a sudden there were all these games out there, and now it's disrupting the handheld gaming industry." We've seen a few hints, mostly in commercials and rumors, that Apple has been looking at the iPhone and specifically at the iPod touch as a gaming platform, but Citron believes the wind has changed for good. "I don't think they're thinking of it as an accidental opportunity any more. I think they're diving in headfirst."
And considering all the mentions regarding the iPhone (and thus the App Store) being more successful than Nintendo's DS and Sony's PSP as a gaming device, I definitely agree that Apple is seeing this a huge opportunity.