iPhone 4 & iOS 7 keyboard lag fix
If you updated your iPhone 4 to iOS 7 and find your device unusable because of ridiculous keyboard lag, put that hammer back into the toolbox.
There is a simple fix that, so the rumour, works for everyone:
on your iPhone 4 go to Settings => iCloud and disable "Documents and Data".
For extra luck reboot, and whoooooosh - your keyboard should be behaving correctly.
Don't take my word, though. Read more => http://news.softpedia.com/news/Guide-Fix-iOS-7-Keyboard-Lag-on-iPhone-4-385447.shtml