The final design factor is very important to us, for it is the essence of all but is virtually never addressed: How do we define SUCCESS?
Ask this question and you will be surprised by the variety of responses. Where one would expect almost exclusively financial gain to be the answer sit a wide range of different motives many of which personal (some even with pathological features).
Put simply success usually happens when the business model is effectively executed. So what is the business model? What purpose does it serve? A little exercise with the Business Model Canvas (created by Osterwalder/Pigneur) can help bring clarity to this question.
If you asked us, we would define success as: a good acceptance in the market, strong sales and a good usability for the end consumer. But these things are extremely dependent on many factors and so we often measure our success based on the acceptance of design awards.
The clearest answer is obtained if one asks: What inspires me? Knowing what creates enthusiasm is vital component in a design project.