Game Center has 67 million users
At the previous iOS 5 press conference, it got about 30 seconds of cverage in a two hour event; something that's not been particularly improved upon in the current event.
Still, Scott Forstall did reveal that the platform now has 67 million users.
There's no easy way to work out what conversion rate this is.
Apple has sold around 250 million iOS devices in total , but Game Center only supports iPhone 3GS and above, so the rate will be well above the core 26 percent rate.
Given more than 70 million iPhone units had been shipped to retail since iPhone 4's launch in June 2010, that 67 million number would seem to suggest a rate in the range of a half to a third of iOS users have set up a Game Center account.
In absolute terms, iOS/Android cross-platform mobile gaming network OpenFeint currently claims around 120 million users.