- No devops, you have real sysadmins whose priority is security and system administration, not development.
- Not relearning to invent the wheel every six months. The technology changes incrementally. If you get out of the field for a few years, read the "what's new" sections of the new manuals to catch up.
- Documentation. IBM docs are great, remind me of NASA docs. They have everything you need, you can go days without googling a problem.
- Backwards compatibility. Decades old sources can be compiled, decades old binaries can be run. Architecture changes are handled transparently.
- Simplicity. The interfaces might seem primitive compared to PC OSs, but there's also less complexity, and less attack surface.
- Uptime. Almost everything, including CPUs, is hot-swappable. This doesn't add to the joy, but it's remarkable.