This is the best comment so far, I think, because it highlights why a designer + engineer, even a theoretical 'designeneer' equally skilled at both, isn't neces

This is the best comment so far, I think, because it highlights why a designer + engineer, even a theoretical 'designeneer' equally skilled at both, isn't necessarily going to be twice as valuable, and in fact may be only as valuable as a single engineer or a single designer. I believe strongly in the value that knowing both can give you, and for certain classes of small project it's a huge win. But you're right: context-switching is a limiter. You only have so much free time and mental energy. For me, I know that I prefer working with competent UX/visual design guidance. I can get some really pretty results from doing my own designs, but it's a wonderful freedom to know that I'll spend 15 minutes in the morning iterating on a piece of paper with a designer today, and then just go away and do my thing. I'll get a PSD that will make the prototype UI more concrete late-afternoon, and the next morning we can talk about how using the UI makes us want to change it. But if I was doing it all myself? I doubt that even with twice the time, the overall result would be equal, either on the code or the design side. That designer keeps all of his visual design acumen and photoshop 'muscle memory' loaded into cache. I keep my emacs key-chords, the code's secret sauce, my bash and git aliases and the topography of staging environments loaded into my cache. There are definitely projects that exist where you can 'do it all', but ... node.js' model is great for maximizing throughput, but when you've got drastically different types of work, that's what you have multiple cores for. ;)