[degusta]

Here's an animation/toggle I did comparing Roboto & Helvetica: http://und.st/pqCj4I.

In the lowercase, there are only 5 letters (a, e, f, g, k) that a normal person would have much chance of distinguishing, even some of those are subtle. The other 21 letters appear virtually identical.

[AllenKids]

http://i.imgur.com/wa7F7.png

I stumbled on upper case "I"s and some others, but generally, it's not really hard to see the slight ugliness.

[degusta]

Haha well said (& well done).