User friendliness - a matter of taste?

Sneaking about on the WWW I tend to find all these articles dealing with something the authors call user friendliness in computer programs. Most of the articles deal in the differences between the OS X interface and the Windows interface. But they often tend to generalize, thereby and hence talking about user interface design in general. And that's nice, that people care about how things look, but that's also the problem. 90% of the articles dealing in user interface design focus on visual design. Now, visual design is only a small part of the user interface. Indulge me while I explain why it's important to know this.

User interface design is not if that button should be red or blue, or it's that too, but not only. The isolation of visual elements is called graphical design, which is something quite different from user interface design. Since my field of interest lie within the world of RIA applications, I'll use this as my point of origin for this statement.
When you sit down on your trusted behind and start thinking about how your RIA application should behave, you need to take into consideration the following elements: IA/SD, UID/HMI and GD. So, that's a lot of nice not disclosing concepts, here's what they mean.

IA - Information architecture. SD - System design(systemization):
In RIA development, these two are actually the same thing. In other areas like website development, IA will adhere to a slightly different path than SD, but in most cases, and in this case, they are the same thing.
The science of expressing a model or a concept of an entire system is the shortest possible definition of these concept I cold come up with on the fly. This means using a modeling approach to break down large amounts of data to a more readable format in which logical paths of data can be seen in the development and design of the application. In others words, trying to predict the users movement trough the system. This approach lays the foundation for usability and findability in applications, websites and databases.

UID - User interface design. HMI - Human machine interaction:
Like IA and SD, UID and HMI also go hand in hand, the only difference lies in more empirical approach of UID, while HMI is much more theoretical. UID is, as the expression denotes, a collection of rules on how to design the user interface of your application, like buttons and boxes and stuff. The rules that make up UID are derived from HMI principles, like Fitts' law, reaction time and so forth. Let me stress this point, these rules are measurable data, it is not a matter of taste. The HMI principles are built upon years of research into human physiology, psychology and human habits. So when the UID principle state that the OS X menubar on the top of the screen is a better way to go than attaching the menubar to each and every window(Windows), we know this because we can actually prove it trough a HMI principle. And therefor we simply adheres to the UID/HMI principles when designing an interface.

GD - Graphical design:
This is not a matter of taste either. Surprised? Well, GD is kinda a matter of taste, but there are lot's of rules in this area too. It's a reason why you are reading this black text on a white background you know. Graphical designers knows that this work, and they stick to it most of the time. In this area you encounter subjects like readability, fonts and so on. But do not get me wrong, graphical designers do not only deal in colors and fonts, they also need to know stuff from the UID area, how else would that know how to design a button that the user actually will understand how to click.. The transition between UID and GD is blurred, and I think it should be. The result of all these fields coming together will result in a efficient, understandable, beautiful and intuitive user interface.

So here is my point in all of this. You cannot simply look at an application and say that it's ugly and therefore it must it can't be user friendly.. it may very well be extremely user friendly. And then again, a really pretty application with fancy stuff in it may be completely useless. User friendliness is not a matter of taste, it's a matter of skill and knowledge, plus a touch of magic.