There is a warning for iPhone 4 users with the new version of iTunes that will be coming out version 11.1. Apparently Apple has turned off the ability to restore to custom firmware using itunes if you have already updated to iOS 7.
Someone mentioned this on a youtube video while discussing the new jailbreak for iOS 6.1.4 and the future jailbreak for 7.
I've seen iOS 7 on an iPhone 4 just today (Verizon 3G) - and right away wished for maple syrup. (That's right - it looked pancake-flat, likely due to the non-Retina display of the iPhone 4 by default.)
I am hoping it does not look as flat on an iPad.
The iPhone 4 does have a Retina display as does the iPod touch 4.... But isn't that the point of iOS7 to be a flatter OS? To get rid of the gradients, etc.