For some Solaris has been one of the first UNIX experiences, as it was one of the most popular unices out there. Most university used it before Linux became popular.
For others, like me, who learned Solaris fairly late (2006), Solaris was a testbed for one of the best operating system technologies out there. Modern filesystem (ZFS), dynamic tracing (dtrace), containerization (zones), dependency management during boot (svc) and virtual network stack (crossbow), have been in solaris way before Linux. Most of modern Linux tools, such as eBPF, systap, btrfs, etc are a direct answer to the research done by Sun.
So some are nostalgic as it's their first experience, others, because it felt like a really good operating system a few years ago (despite it's quirks).
For others, like me, who learned Solaris fairly late (2006), Solaris was a testbed for one of the best operating system technologies out there. Modern filesystem (ZFS), dynamic tracing (dtrace), containerization (zones), dependency management during boot (svc) and virtual network stack (crossbow), have been in solaris way before Linux. Most of modern Linux tools, such as eBPF, systap, btrfs, etc are a direct answer to the research done by Sun.
So some are nostalgic as it's their first experience, others, because it felt like a really good operating system a few years ago (despite it's quirks).