Usability and user experience

I very much appreciated Graham’s description of the difference between “usability” and “user experience”. At this stage it’s the type of thing that should seem quite obvious but it’s often overlooked when looking at HCI as a whole. From looking around, some definitions I have found are:

The extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use.

- UsabilityNet, the ISO 9241-11 standard

Usability means that the people who use the product can do so quickly and easily to accomplish their own tasks.

- Janice Redish and Joseph Dumas, A Practical Guide to Usability Testing

After all, usability really just means that making sure that something works well: that a person of average (or even below average) ability and experience can use the thing - whether it's a Web site, a fighter jet, or a revolving door - for its intended purpose without getting hopelessly frustrated.

- Steve Krug, Don't Make Me Think

Or as one person has put it - good usability is when someone turns to their friends and says “look at this, it’s awesome!”.

I would say that good usability is when the target user is able to complete their task to their satisfaction i.e. quickly, simply, with as little pain as possible.

Regarding user experience, Don Norman puts it very well:

In reality a product is all about the experience. It is about discovery, purchase, anticipation, opening the package, the very first usage. It is also about continued usage, learning, the need for assistance, updating, maintenance, supplies, and eventual renewal in the form of disposal or exchange.

I would say that this is more intangible that usability, which can be more easily measured. User experience is about how people feel about the product, whether they have a good time using it or not.

Both are obviously important to consider in design and development, and I feel that the distinction between the two should be more clear to those involved.