One of the most dreaded things being a user of any software application is the training and learning process one has to go through. The company pays for your courses. But if you're an independent, you have to go out there to learn it yourself.
Being and interface designer isn't any different either, especially if you're looking to redesign any interface. From my experience and my opinion, if the documentation or training course has more than 25 pages, the application is probably too complex to learn quickly.
There are many times where I come across a current design ready for revamping, and the interface tells me very little, or rather a lot - too much in fact because at that point, I've already assessed it to being too complex to learn in 30 minutes or less.
Some factors that prevent quick learning:
1. The documentation is the tutorial. They are usually too long and too complex to understand;
2. The interface was designed poorly. This is usually a case of when usability is still in at its infant stage;
3. The application is not focussed. Usually is the case when a set of target users is too broad or inappropriate.
I could go on, but then like some long documentation, I'd lose your interest.
So to solve all this, why not let the interface tell the story? Have the development processes integrate such a way that enables pre-development work. This also includes focusing your target users and developing mental models - a translation between the human being and software system. So that once actually concepts are being developed, the end in mind is always letting the interface tell the user how they want to be operated upon.
Of course, a lot of past experiences would have to be harnessed. This is what we call "intuitive". (That could also be another debate.) At least in this case, documentation is lessened, the training is made easier and simpler to follow. It would definitely make life a lot easier.