What makes a design great?
Steve Jobs once said that design is not just what it looks like and feels like. Design is how it works. One of the other pieces that help make it work is the feeling.
If there's consistency in the mood that it creates and whether or not that mood evokes the proper emotional response from the intended audience. Donald A Norman once said, Everything has a personality. Everything sends an emotional signal. Even where this was not the intention of the designer, the people who view the website infer personalities and experience emotions.
The final element in the F3 rule is function. Function refers to how something works and whether or not it serves its intended purpose. That means being easy to read and understand and also that the form is executable within the given medium in which it was presented.
That's very true. You should always be aware of what your design is supposed to do and where it's supposed to go once it leaves your desk. Keep that in the back of your head throughout the design process so you can better match the form to the intended function of the finished product.