As of now Apple has no officially supported way of downgrading an iPhone 4 or 4S back to iOS 5 if you've already upgraded to iOS 6. So if you're unsure if you want to upgrade to iOS 6 or not, you might want to checking a local store or have a buddy with iOS 6 available to test it out before trying it out on your own device.
Allen
Google Nexus 4 / Google Nexus 7
