Just found it on my iPhone this morning, but I may wait a few days to upgrade for safety. It's a bit annoying that I don't get a say whether I want to download the upgrade or not.
I do hope that this upgrade will end the game center harassment. I had to register to the damn thing to get rid of endless error messages, and now it welcomes me back every single time I open a game app, just to rub it in. Leave me alone, Apple!