In the app it responds to whether or not you've locked screen rotation, which I do--to portrait.

It would be nice to have the option, since many people prefer the landscape keyboard, or don't want it to switch if they're already in landscape mode.

I, on the other hand, have a large phone in a big case, and the landscape keyboard is much less comfortable than the portrait one. I'd like to be able to choose portrait all the time, so I can quick reply to messages, even if I'm lying on my side.