Touch-typing on any little keyboard like that is near impossible. On a normal keyboard, you're moving multiple fingers short distances. While on a little keyboard you're moving two fingers longer distances (key-wise, not actual distance). This makes it much harder to touch type since it's harder to judge where your fingers have to go.
This is at least my experience with little cellphone hard-keyboards, maybe it's different for others.
Regardless, braille would be really cool. Assuming the screens were high enough resolution (that is, could raise itself up accurately enough to make small dots) to display it.
I've taught myself to type without looking on my Android (holding it portrait too, not landscape). I do rely pretty heavily on the auto-correct feature to help prevent gibberish, though.
Braille would be easy to implement too, both Android and iOS control fonts at the system level (well, usually on Android) so all you have to do is add a Braille font and you're done.
This is at least my experience with little cellphone hard-keyboards, maybe it's different for others.
Regardless, braille would be really cool. Assuming the screens were high enough resolution (that is, could raise itself up accurately enough to make small dots) to display it.