One issue on the HTC One that has been fixed dealt with SwiftKey's Swype-styled "Flow" and included problems with the trail that follows a user's finger from letter to letter. Another fix on the Taiwan based manufacturer's new flagship model now allows users to type in the HTC OneNotes app while another fix turned word prediction back on for Android 4.1. Bugs that affected typing on the HTC One stock mail client are now gone.
For other Android models beside the HTC One, version 4.0.1 of SwiftKey improves the prediction quality of the app while also fixing a problem that made the cursor jumpy on the calculator of certain Samsung devices. Also, the various bugs that were causing the keyboard to crash while performing certain applications are now removed. Overall, you should enjoy a better typing experience with the app following the update.
source: SwiftKey via AndroidCentral