Although I've used Windows, various Linux distributions and two BSD flavors, I'm not going to comment about them as they worked well for me but, what I can tell you, is that I've chosen NetBSD as my main and only operating system.
The reasons I like NetBSD:
- It's easy to install;
- Good documentation. Whenever I needed to solve something, it was available in the documentation or the FAQ, I never had to Google for anything that was related to the operating system;
- I like the fact that, when I install my system, all I get is the operating system ... nothing more, nothing less;
- Related to the point above, I like the package modularity it offers (I enjoy the pkg_* tools) and the fact that no 3rd-party package gets installed unless I say so. It works with or without them. I come from a Windows background and I was amazed by the fact that, on UNIX-like systems, I don't need nor have to reinstall an application if some component is outdated, I only have to update the outdated component. Two thumbs up for the Packages Collection;
- And finally, I like the fact that I never had any true problems using it nor configuring it and, although I don't remember having any issues, they were probably RTFM-related;
I'm sorry for not stating any power-user reasons like those given in the previous comments but from my point of view, it's OK.
One of the key characteristics of NetBSD is that its developers are not satisfied with partial implementations. Some systems seem to have the philosophy of “If it works, it's right”. In that light NetBSD's philosophy could be described as “It doesn't work unless it's right”.
: If I were to choose a non-BSD operating system, my first and only choice would be Slackware. It's simple, robust and I'm not afraid to get down-and-dirty configuring it. Same goes for NetBSD.