Dont worry about it too much. I use the 8900. I am on tmobile. I use font size 14. After using the 8900 for a few weeks you tend to know where the keys are. Letter D and letter J are perforated keys so that they act as your guiding stars as to where the rest of the keys are on the keypad.
Finally I am partially sighted and doing absolutely well with the 8900. So go for it.
Also have a look at the 9000 Bold. My personal view is that it is better than the 8900. It is more feature rich but is a touch too big for my liking.
Hope this helps!
Amod Wadhi Blackberry Support Specialist http://chumedh.com No more outsmarting smartphones!!...We will fix it!