Whenever a new iOS is launched there are always issues, this is because the beta version is only available to a limited number of people, and they cannot come across all the problems that lie dormant. It is for this very reason why some iPad users are having iOS 7 keyboard lag issues.
Apple and its iOS system is known for how responsive the software is, so it is a huge problem when some users experience an unresponsive keyboard or even lag. From what is being reported on Apple Support Communities, all iPads updated to iOS 7 suffer from this bug.
However, we can tell you that there is a fix for these keyboard lag issues on the iPad. All you have to do is go to Settings, iCloud, then turn Documents & Data to off, then back on. You then need to go to General and select Reset, followed by Reset All Settings. The final step is to reconfigure your keyboard; this will allow your iPad to restore your keyboard so that it functions normally.
This fix is not working for everyone and so the only other choice available is to restore the iPad. We know this is a last resort, but it is the one that usually fixes issues like these. If the iOS 7 keyboard lag issues on iPad continue after that process, then you will have to wait for iOS 7.1, which we expect to be announced during Apple’s event next Tuesday.
One of the biggest issues to have hit iOS 7 is with iMessage, and even though the issue has now been resolved, there are still times when messages do not send. However, it is not as often as before.
Also See: iOS 9 OTA beta 3 update notes live