The author, Justin Mifsud, must be a bit of a geek (or an academic!) judging by the number of articles he faithfully references in this piece.
But it is worth a quick read as he does a good job of explaining the relationship between activities such as marketing, design, ergonomics and usability - part of the range of expertise that goes together to make a great (or rotten) user experience.
I particularly liked this diagram, which comes from a 2008 Nielsen Norman Group conference.
|Usability and user experience|
The difference (and relationship) between usability and use experience - article by Justin Mifsud for usabilitygeek.com
Justin also references a fantastic scenario by Jared Spool which I think illustrates the relationship far better than any diagram or definition. In this blog post, Jared tells the story of someone buying a camera online without any problems at all (great website usability) and then has a complete nightmare when she goes to pick it up from the local store later the same day (terrible customer experience).
Related - accessibility and usability
Justin also wrote a related post which is also a good read when considering the context of usability: