The gkos keyboard is good for writing short phrases. You write one and then copy and paste it into your document, which is in another program. I imagine you would then clear the gkos buffer and start a new or connected thought.
There are two layouts, alphabetic and optimized. I'm giving the optimized one a try; since it's based on key combination frequencies it should be more ergonomic. I'll probably give the alpha a try as well.
So far I haven't built up much speed, but I've only been using it for one day. My progress in this time convinces me speed will come with practice.