Comment by WayneDB

You can absolutely pass valid judgement on quality of usability on sight alone.

If I showed you a picture of a 4 foot wide ship wheel and said I was going to install it in my Mazda Miata - you'd know instantly that it would be unusable, right? How about a screen-shot of a text editor that only shows you one giant character at a time?

Even as we move away from the ridiculous end of the spectrum of examples - you can know how usable something is based on past experience with similar environments.