iOS 7 on the iPhone 4 is practically unusable. Much like the iPhone 3G was with a previous iOS version (5 or 6, I can't remember). As much as people in here are screaming "get with the times," I can understand somebody not willing to update to preserve their device functionality. At the very least, Apple should include an option in the software update settings to turn this on or off, and if you turn it off after the download of the new OS, it should delete the update and free up the storage on the device. That's not exactly rocket science. And if the person decides to upgrade to the new iOS at a later time, they can sit through the download process at that point in time.
iOS 7 on the iPhone 4 is NOTHING like iOS 4 on the iPhone 3G. My iPhone 4 is on iOS7, and still runs fine. Sure it is a slower than when it had iOS 4, but no change in speed from iOS 6.