I find it strange, that SwiftKey is so fast to say on their website, that problem with their keyboard not appearing, disappearing, not working, crashing and etc is because of bugs in iOS - yet, with Swype, I have not encountered one single of the bugs.
I re-installed SwiftKey (thought that hey, maybe I was just too critical) and literally the first time I was to use the keyboard (in iMessage) first it didn't appear. Afterwards, when I got it to appear, it crashed as soon as I tried to go into the character-selection...
Seconds later, SwiftKey was uninstalled and I was back to using Swype.
EDIT: This is in no way meant as a bashing for SwiftKey or and ad for Swype - I actually prefer SwiftKey, but it's so unstable and so utterly useless at the moment, it's sad, really...