Usability fundamentally means you can quickly do what you want, instinctively with no training, getting exactly what you expect. Simple no?
And then there's reality.
Let's take the example of transportation. A bus, train, or plane is very usable. In 30 seconds someone can figure out how to use it and get on the appropriate vehicle. Works great if it starts where you are and ends where you want to go. So we give this an A+ on ease of learning. But it has an F on usefulness if it's routes don't match your needs.
Then we have the automobile. Anyone who has taught their children to drive realizes that driving a car is not intuitive. It's tens of hours of lessons, the onset of grey hair, and at times wondering if they'll ever be competent. So a C on ease of learning. But an A+ on usefulness as it can take you directly to where you want to go.
And the funny thing is, once we're used to driving we find it intuitive, useful, simple, and very powerful. This is the definition of well designed usability.
We faced this same conundrum designing the query wizards in our Designer. Users want to be able to select any data and they want to be able to instantly know how to do so.
On the instantly usable approach, a programmer creates the datasets that can be used designing a template and the designer then just drags the desired data into their template. Intuitive, usable, and very limited. If you have all the data you need this way - it's great. If you need something more, you're screwed.
On the select any data approach, the designer can write their own queries. This has a learning curve but the designer can then select any data they wish. No limitations.
What we did with Windward is we created wizards that could be used to create 100% of the queries 98% of our customers need to write. That 2% allowed us to keep the wizards straightforward (and that 2% can write their occasional very complex query by hand).
We also took the approach that it will require 5 - 15 minutes to learn. And in return for that requirement, users then have a tool that is easy, powerful, and fast. It's a trade-off, but a 5 - 15 minute investment in return for something that is then this marvelous easy approach day after day, year after year - well worth it.
So to us exceptional usability is like driving a car, it may require a small investment in learning. But then you have something that is intuitive and very powerful. And unlike learning to drive a car - no grey hair.
Oh, and for those that do prefer the instantly usable pre-defined data approach, Windward has both PODs and Datasets. With these someone else defines the components (PODs) & structured obvious data (Datasets) and the designer just drags them. And when that fits a designer's needs - it's a wonderful approach.