3d modelling is a problem domain where performance is the most important feature. Without sufficient performance, the tool.is not interactive. And direct interaction with immediate visual feedback is the whole point of these programs.
Having worked in 3D, including tools, it's my experience that features and productivity (=program is delivered on time) are the most important features :)
The code needs to be "fast enough"¹. Though this often means more attention to speed than in other kinds of software. To rephrase, speed is often necessary but not sufficient to make good tools.
¹ I try to avoid using "execution speed" and "performance" interchangeably, since a crashing, late or incorrect fast program is not a well performing program!
Fair point. Let me rephrase my point of view a little: you haven't made the users truely productive unless the tools are able to provide responsive and accurate interactive feedback. Anything that causes feedback to be non-immediate makes it harder for the user to dial in the exact results they want. They have to spend more time and give up when they have reached an inferior result that meets basic quality standards. Smooth and direct interaction makes them go the extra mile while enjoying the process.
The app is Dust3D, a ease-of-use focused mesh editor which deals with simple meshes.
Certainly from the blog post you get the impression that programmer productivity is a consideration in his choice of language.