You don't have to be a geek to understand usability.  By definition, we play a daily part in user experiences and, therefore, usability.  Think about it.  You buy a new set of drinking glasses because they appeal to your taste, they match your kitchen, and they complete your dinner table spread nicely.  But just how user-friendly are those glasses?  The thickness of the glass or shape of the lip may make for an interesting game of 'sip and spill' without careful execution!  While some may argue that this is not a problem in usability, but rather a design issue, it can be proven by simple everyday scenarios that it is both. 

Designs, whether good or bad, create user experiences.  A poor user experience may call for design modifications to be made with the intent of enhancing the user's experience going forward.  The easier it is for a consumer to utilize the design, the tool, the drinking glass, the better the outcome or end goal.  This is usability. 

It is important not to confuse bad usability with lack of understanding the goal or simply lack of reading instructions!  After a poor user experience it is not difficult to inflict our opinions on bad usability.  Maybe just employ the rule of the drinking glass:  Chances are, if you have trouble drinking from a glass like this, others will too.  However, if you simply failed to read the manual before setting up the new DVR to record for the first time, don't blame the cable network just yet!