I agree with you, my eyesight is /terrible/, even with strong prescription glasses (gogo +10) I find myself squinting at tiny fonts and when I drawn I lean reeeeeeeeeeally close to the screen so I can see the details easier without having to zoom in too far.
Fully scalable UI will benefit me greatly (as it has done with other games that have a scalable UI), mostly the chatlog side of things so I can reed teh wurdz, but hell even minimaps and the like too!
I'm really excited to see what it's like~ blind peoples, represent! XD