The Set Book assignment should enable you to begin talking about the usability of interactive products in terms of a variety of parameters. Instead of simply saying 'nice cell phone, lovely to use' or 'awful MP3 player, really bad design' you should now be equipped (having studied Unit 2) with a set of terms and concepts that can help you describe what is good and bad about an interactive product'sdesigninterms of usability.
However, it is still easy to fall into the trap of talking about usability at a fairly shallow level. For example, when asked to do this exercise, you may have just said 'product X is easy to use, remember and learn'. This may be the case, but you need to explain why. You need to explore in more depth why you think something is usable or not, in terms of A, B or C. In so doing, you may find that while the basic functions are easyt ol earn,m anyo ft hemoreadvancedfunctions arefiddlyor inefficient to learn how to use and remember. Hence, a product's usability will vary depending on the nature of the task, the context in which it is being used, and who is using it. Setting specific questions for each of the usability and user experience goals and the design concepts can help you to start articulating in more detail what is and isn't usable about a product (and why this is the case). In addition, asking someone else to try doing a range of tasks and observing them can be very revealing, showing you aspects that you would overlook yourself or take for granted.
You should also try to avoid seeing usability in terms of 'black and white', i.e. a product is either easy to use or not, it is efficient or inefficient to use. What is often much more interesting are the grey areas, where it may notbeobviousa t firstthattherei sap roblemb utonlyafter careful examination are you able to identify a specific usability problem (or set of problems).