2 years using Messagease keyboard (like Thumbkey keyboard) but not opensource. Recently (3 months ago) I switch to Thumbkey, I admit they both use a crazy layout, it takes time to lear, it but now I am quite fast with it and I would not switch back to a qwerty layout. Despite I recommend to give it a try, it is not for everyone. However, no matter what keyboard you choose, but choose an opensource keyboard if you want to stay private.