One of the features of UNIX was that it was designed by taking a few very simple ideas and more importantly simple constructs, and then building more complex constructs out of them. It made it possible for a handful of researchers to write all the bits of an OS needed to get to a multi-user prompt. Which at the time other examples had giant teams of engineers associated with them. That made it easy to understand at a fundamental level and you could reason about the effects various things would have on it should you make them.
One of my favorite books is "Operating Systems Concepts" which has a great survey of the features of any good operating system.
So is being Unix-like better? Yes if you want a simple robust operating system. No if you want a hard real-time operating system. Yes if you want a system you can flexibly add devices too. No if you want to build a security model based on capabilities. Yes if you want it to work on a small architectures with stack support. No if your processor doesn't support stacks or the C model of frame pointers.
In general though understanding what an Operating system has to do is priceless for a CS person to have in their toolkit.
If you need a yacht that can carry many people on the high seas through bad weather at speed, unix is solid. But there hasn't been a great racing dinghy since the 80s.
Maybe there is an demoscene/hacking tradition out there, waiting for to be discovered.
Consider the debates that we don't have:
* Hardware abstraction. Casual audio programming is harder now than it was twenty years ago. Also - why doesn't hardware self-describe?
* High-level languages. Chuck Moore's ideas of code bloat are on a totally different level to the mainstream. He's onto something.
* Protected memory. Does it matter on a machine designed for fun? How much more hackable could your OS be if you got rid of stuff like this?
Stability doesn't matter so much in fun systems. If you're in a dinghy and not capsizing, you're not sailing hard enough.
http://valerieaurora.org/synthesis/SynthesisOS/
Also, there was something about Arthur Whitney looking to build a stand-alone OS in/under K recently.
Thanks - looks awesome. I particularly like his approach to HTML.
UNIX-like includes philosophies such as "almost everything is a file" and "use human-readable (and writable!) plain text formats by default" and "there will be a stdin, stdout, and stderr; use them all". More than anything else, I think that a UNIX is defined by the idea that any end-user might decide to become a programmer at any moment, and this is OK and perhaps even desirable.
Very, very desirable in my view; in contrast to the raging trend of simplification/hiding going on these days, trying to turn computers into sealed-box appliances "you're not supposed to know how it works" that give little in the way of things that can get people interested in learning more about them, I find classic UNIX to be very open in encouraging users to learn more about the system.
(Myself, I moved to FreeBSD a while ago).