Productive software developer
A productive developer and programmer is someone who understand the economic driver of his/her company. He understands that it is his sworn duty to develop a software that offer some values to the user. A developer must continuously ask himself:
Is my code offers any value to the user?. Did my commit at the end of each day really make a different in customer's life ?
It is easy for software developer to become obsessed with the technology and code behind their application, which sometimes offer absolutely nothing to the end user. I make this mistakes all the time. As engineers, more often that not, our design is driven by our own persuit of technical glory rather than actual end user needs. 37Signals guys, in a way have mastered the art of giving end user what they want, and keeping out code that offers little value.
How do we give the user what they want?. Unfortunately, this isn't very easy. We need to leave our selfish technical brain, put on a user hat and ask some honest questions. Why do my customer buy my software and what exactly are they looking for? It is far too easy to let the engineer inside us to offer a cool solution to a non-existence problem. Remember that our technical expertise is there to solve user's problem and not to add new problems by cluttering the software with tons of rubbish code.