When Game Center was first announced way back in April, the first question everyone had was about all of the third-party networks that had already built up in the space. OpenFeint was the biggest of these, and founder Jason Citron had no apparent worries about Apple's advance into social gaming -- he said that OpenFeint would continue to offer features beyond what Game Center did, and that developers would be easily able to use both networks in their apps. A report released last week by OpenFeint says that's exactly what's happened -- the userbase has doubled to a whopping 50 million users since Game Center launched, and games on the network have also increased 119% since Game Center was announced.
Those are pretty amazing numbers -- there was a lot of talk earlier this year that Apple would walk into this space and just dominate (and certainly, I've seen a lot of solid Game Center integration since release, and of course because Game Center is automatically installed in iOS, adoption is probably huge), but that hasn't been the case at all. There's definitely room for services like Plus+ and OpenFeint, even with an official network up and running. OpenFeint, as far as I've been told, is also still planning the OpenFeint X service, with more options for in-game microtransactions, so we'll have to see what they're up to next.